Bovine foamy virus (BFV), a member of the spumavirus subfamily of retroviruses,contains two open reading frames (ORF-1 and ORF-2) in addition to the genes coding for gag,po/and env. Borf-1 protein, encoded by BFV ORF-...Bovine foamy virus (BFV), a member of the spumavirus subfamily of retroviruses,contains two open reading frames (ORF-1 and ORF-2) in addition to the genes coding for gag,po/and env. Borf-1 protein, encoded by BFV ORF-1, is identified as a transcriptional transactivator, which augments gene expression directed by the viral long terminal repeat (LTR).Further investigations in transient expression assays reveal that the Borf-1 responsive elements are located in the U3 domain of the LTR, upstream from position -140 ( + 1 represents the transcription initiation site), and the BFV RU5 region has an inhibitory effect in LTR-directed gene expression.展开更多
Cell cycle progression is regulated by interactions between cyclins and cyclin-dependent kinases (CDKs). p21(WAF1) is one of the CIP/KIP family which inhibits CDKs activity. Increased expression of p21(WAF1) may play ...Cell cycle progression is regulated by interactions between cyclins and cyclin-dependent kinases (CDKs). p21(WAF1) is one of the CIP/KIP family which inhibits CDKs activity. Increased expression of p21(WAF1) may play an important role in the growth arrest induced in transformed cells. Although the stability of the p21( WAF1) mRNA could be altered by different signals, cell differentiation and numerous influencing factors. However, recent studies suggest that two known mechanisms of epigenesis, i.e.gene inactivation by methylation in promoter region and changes to an inactive chromatin by histone deacetylation, seem to be the best candidate mechanisms for inactivation of p21( WAF1). To date, almost no coding region p21(WAF1) mutations have been found in tumor cells, despite extensive screening of hundreds of various tumors. Hypermethylation of the p21(WAF1) promoter region may represent an alternative mechanism by which the p21(WAF1/CIP1) gene can be inactivated. The reduction of cellular DNMT protein levels also induces a corresponding rapid increase in the cell cycle regulator p21(WAF1) protein demonstrating a regulatory link between DNMT and p21(WAF1) which is independent of methylation of DNA. Both histone hyperacetylation and hypoacetylation appear to be important in the carcinoma process, and induction of the p21(WAF1) gene by histone hyperacetylation may be a mechanism by which dietary fiber prevents carcinogenesis. Here, we review the influence of histone acetylation and DNA methylation on p21(WAF1) transcription, and affection of pathways or factors associated such as p 53, E2A, Sp1 as well as several histone deacetylation inhibitors.展开更多
After reverse transcription, the HIV-1 proviral DNA is integrated into the host genome and thus subjected to transcription by the host RNA polymerase Ⅱ （Pol Ⅱ）. With the identification and characterization of huma...After reverse transcription, the HIV-1 proviral DNA is integrated into the host genome and thus subjected to transcription by the host RNA polymerase Ⅱ （Pol Ⅱ）. With the identification and characterization of human P-TEFb in the late 1990s as a specific host cofactor required for HIV-1 transcription, it is now believed that the elongation stage of Pol Ⅱ transcription plays a particularly important role in regulating HIV-1 gene expression. HIV-1 uses a sophisticated scheme to recruit human P-TEFb and other cofactors to the viral long terminal repeat （LTR） to produce full-length HIV-1 transcripts. In this process, P-TEFb is regulated by the reversible association with various transcription factors/ cofactors to form several multi-subunit complexes （e.g., 7SK snRNP, super elongation complexes （SECs）, and the Brd4-P-TEFb complex） that collectively constitute a P-TEFb network for controlling cellular and HIV-1 transcription. Recent progresses in HIV-1 transcription were reviewed in the paper, with the emphasis on the mechanism and factors that control HIV-1 transcription and latency activation.展开更多
PURPOSE: To review the recent developments in the structure and function of Smad proteins. DATA SOURCES: Both Chinese- and English-language literatures were searched using MEDLINE/CD-ROM (1997 - 2000) and the Index of...PURPOSE: To review the recent developments in the structure and function of Smad proteins. DATA SOURCES: Both Chinese- and English-language literatures were searched using MEDLINE/CD-ROM (1997 - 2000) and the Index of Chinese-Language Literature (1997 - 2000). STUDY SELECTION: Data from published articles about TGF-beta signal transduction in recent domestic and foreign literature were selected. DATA EXTRACTION: Data were mainly extracted from 22 articles which are listed in the reference section of this review. RESULTS: Smad proteins mediate signal transduction induced by the TGF-beta superfamily. Based on their structural and functional properties, Smad proteins are divided into three groups. The first group, receptor-regulated Smads (R-Smads), are phosphorylated by activated type I receptors and form heteromeric complexes with the second group of Smads, common mediator Smads (Co-Smads). These Smad complexes translocate into the nucleus to influence gene transcription. Inhibitory Smads (I-Smads) are the third group and these antagonize the activity of R-Smads. In the nucleus, Smads can directly contact Smad-binding elements (SBE) in target gene promoters. Through interaction with different transcription factors, transcriptional co-activators or co-repressors, Smads elicit different effects in various cell types. The aberrance of Smad proteins has been noted in several human disorders such as fibrosis, hypertrophic scarring and cancer. CONCLUSION: The structure of Smads determines their function as transcriptional factors which translocate signals from the cell surface to the nucleus where Smads regulate TGF-beta superfamily-dependent gene expression.展开更多
Objective To determine the in vitro expression of interleukin-12 (IL-12) and its effect on signal transducers and activators of transcription (STAT) signaling molecules in peripheral blood mononuclear cells (PBMCs) in...Objective To determine the in vitro expression of interleukin-12 (IL-12) and its effect on signal transducers and activators of transcription (STAT) signaling molecules in peripheral blood mononuclear cells (PBMCs) in patients with systemic lupus erythematosus (SLE).Methods Peripheral blood mononuclear cells in 39 patients with definite systemic lupus erythematosus and 11 healthy volunteers were collected. Expression of IL-12 P40mRNA in PBMCs was determined with reverse transcription-polymerase chain reaction (RT-PCR). Quantity of IL-12 protein supernatant was measured by enzyme-linked immunosorbent assay (ELISA). The levels of phosphorylated STAT3 and STAT4 signaling molecules in PBMCs were detected by immunoblot. Results Levels of IL-12 protein and mRNA expression in patients with active or inactive SLE were significantly higher than those in controls. Phytohemagglutinin (PHA) may promote the expression of IL-12. IL-12 alone induced the phosphorylation of STAT3 and STAT4 in PBMCs from patients with SLE, especially in active SLE. However it had no obvious effect on normal PBMCs. Phosphorylated STAT3 and STAT4 might be observed in normal PBMCs treated with IL-12 plus PHA.Conclusion IL-12 is produced aberrantly in patients with SLE. IL-12 might exert its biological role in SLE via the aberrantly phosphorylated STAT3 and STAT4 signaling molecules.展开更多
OBJECTIVE: To clone and study the polymorphism within interleukin-4 (IL-4) proximal promoter of asthmatic children. METHODS: The IL-4 proximal promoter segments were amplified and selected by polymerase chain reaction...OBJECTIVE: To clone and study the polymorphism within interleukin-4 (IL-4) proximal promoter of asthmatic children. METHODS: The IL-4 proximal promoter segments were amplified and selected by polymerase chain reaction (PCR) and single strand conformation polymorphism (SSCP) with genomic DNA from ten healthy children and forty patients with dominantly allergic familial histories as templates. The selected PCR segments were cloned into recombinant plasmids pIL-4-Jx2. The PCR inserts were sequenced by dideoxy chain termination method. RESULTS: Seven aberrant bands were found in SSCP analysis from forty asthmatic patients. The sequencing results showed that four variant sites were found within or adjacent to the known IL-4 regulatory element. A C to A transversion located at -229 position was just within the positive regulatory element-I (PRE-I) in one patient. A C to T transition adjacent to the negative regulatory element-II (NRE-II) and an extra G adjacent to TATA box were found in two patients. A five base nucleotide deletion was found near signal transducers and activators of transcription-6 responsive element (STAT-6 RE) in one patient. CONCLUSION: There were polymorphisms within the IL-4 proximal promoter of allergic asthmatic patients and these polymorphisms might result in aberrant expression of IL-4 gene and asthma.展开更多
Previous studies with deletion and sequence analysis of JDV LTR showed that there is a putative AP-4 responsive element in LTR. By antisense transient assay and gel shifting assay, we for the first time demonstrated t...Previous studies with deletion and sequence analysis of JDV LTR showed that there is a putative AP-4 responsive element in LTR. By antisense transient assay and gel shifting assay, we for the first time demonstrated that AP-4 modulated JDV gene expression by binding DNA di-rectly to bovine cells. The results, derived from site-directed mutagenesis experiments, suggest that the six base pairs of AP-4 binding site (CAGCTG) have different effects on JDV gene expression. When the first two base pairs changed to GC, JDV gene expression is severely decreased.展开更多
文摘Bovine foamy virus (BFV), a member of the spumavirus subfamily of retroviruses,contains two open reading frames (ORF-1 and ORF-2) in addition to the genes coding for gag,po/and env. Borf-1 protein, encoded by BFV ORF-1, is identified as a transcriptional transactivator, which augments gene expression directed by the viral long terminal repeat (LTR).Further investigations in transient expression assays reveal that the Borf-1 responsive elements are located in the U3 domain of the LTR, upstream from position -140 ( + 1 represents the transcription initiation site), and the BFV RU5 region has an inhibitory effect in LTR-directed gene expression.
文摘Cell cycle progression is regulated by interactions between cyclins and cyclin-dependent kinases (CDKs). p21(WAF1) is one of the CIP/KIP family which inhibits CDKs activity. Increased expression of p21(WAF1) may play an important role in the growth arrest induced in transformed cells. Although the stability of the p21( WAF1) mRNA could be altered by different signals, cell differentiation and numerous influencing factors. However, recent studies suggest that two known mechanisms of epigenesis, i.e.gene inactivation by methylation in promoter region and changes to an inactive chromatin by histone deacetylation, seem to be the best candidate mechanisms for inactivation of p21( WAF1). To date, almost no coding region p21(WAF1) mutations have been found in tumor cells, despite extensive screening of hundreds of various tumors. Hypermethylation of the p21(WAF1) promoter region may represent an alternative mechanism by which the p21(WAF1/CIP1) gene can be inactivated. The reduction of cellular DNMT protein levels also induces a corresponding rapid increase in the cell cycle regulator p21(WAF1) protein demonstrating a regulatory link between DNMT and p21(WAF1) which is independent of methylation of DNA. Both histone hyperacetylation and hypoacetylation appear to be important in the carcinoma process, and induction of the p21(WAF1) gene by histone hyperacetylation may be a mechanism by which dietary fiber prevents carcinogenesis. Here, we review the influence of histone acetylation and DNA methylation on p21(WAF1) transcription, and affection of pathways or factors associated such as p 53, E2A, Sp1 as well as several histone deacetylation inhibitors.
基金Project supported by the National Natural Science Foundation of China (No.81201276)the Natural Science Foundation of Fujian Province (No.2012J05067),China
文摘After reverse transcription, the HIV-1 proviral DNA is integrated into the host genome and thus subjected to transcription by the host RNA polymerase Ⅱ （Pol Ⅱ）. With the identification and characterization of human P-TEFb in the late 1990s as a specific host cofactor required for HIV-1 transcription, it is now believed that the elongation stage of Pol Ⅱ transcription plays a particularly important role in regulating HIV-1 gene expression. HIV-1 uses a sophisticated scheme to recruit human P-TEFb and other cofactors to the viral long terminal repeat （LTR） to produce full-length HIV-1 transcripts. In this process, P-TEFb is regulated by the reversible association with various transcription factors/ cofactors to form several multi-subunit complexes （e.g., 7SK snRNP, super elongation complexes （SECs）, and the Brd4-P-TEFb complex） that collectively constitute a P-TEFb network for controlling cellular and HIV-1 transcription. Recent progresses in HIV-1 transcription were reviewed in the paper, with the emphasis on the mechanism and factors that control HIV-1 transcription and latency activation.
基金supported by a grant from the National Natural Science Foundation of China(No．G1999054204)； the National Prominent Youth Science Foundation of China(No．39525024)．
文摘PURPOSE: To review the recent developments in the structure and function of Smad proteins. DATA SOURCES: Both Chinese- and English-language literatures were searched using MEDLINE/CD-ROM (1997 - 2000) and the Index of Chinese-Language Literature (1997 - 2000). STUDY SELECTION: Data from published articles about TGF-beta signal transduction in recent domestic and foreign literature were selected. DATA EXTRACTION: Data were mainly extracted from 22 articles which are listed in the reference section of this review. RESULTS: Smad proteins mediate signal transduction induced by the TGF-beta superfamily. Based on their structural and functional properties, Smad proteins are divided into three groups. The first group, receptor-regulated Smads (R-Smads), are phosphorylated by activated type I receptors and form heteromeric complexes with the second group of Smads, common mediator Smads (Co-Smads). These Smad complexes translocate into the nucleus to influence gene transcription. Inhibitory Smads (I-Smads) are the third group and these antagonize the activity of R-Smads. In the nucleus, Smads can directly contact Smad-binding elements (SBE) in target gene promoters. Through interaction with different transcription factors, transcriptional co-activators or co-repressors, Smads elicit different effects in various cell types. The aberrance of Smad proteins has been noted in several human disorders such as fibrosis, hypertrophic scarring and cancer. CONCLUSION: The structure of Smads determines their function as transcriptional factors which translocate signals from the cell surface to the nucleus where Smads regulate TGF-beta superfamily-dependent gene expression.
文摘Objective To determine the in vitro expression of interleukin-12 (IL-12) and its effect on signal transducers and activators of transcription (STAT) signaling molecules in peripheral blood mononuclear cells (PBMCs) in patients with systemic lupus erythematosus (SLE).Methods Peripheral blood mononuclear cells in 39 patients with definite systemic lupus erythematosus and 11 healthy volunteers were collected. Expression of IL-12 P40mRNA in PBMCs was determined with reverse transcription-polymerase chain reaction (RT-PCR). Quantity of IL-12 protein supernatant was measured by enzyme-linked immunosorbent assay (ELISA). The levels of phosphorylated STAT3 and STAT4 signaling molecules in PBMCs were detected by immunoblot. Results Levels of IL-12 protein and mRNA expression in patients with active or inactive SLE were significantly higher than those in controls. Phytohemagglutinin (PHA) may promote the expression of IL-12. IL-12 alone induced the phosphorylation of STAT3 and STAT4 in PBMCs from patients with SLE, especially in active SLE. However it had no obvious effect on normal PBMCs. Phosphorylated STAT3 and STAT4 might be observed in normal PBMCs treated with IL-12 plus PHA.Conclusion IL-12 is produced aberrantly in patients with SLE. IL-12 might exert its biological role in SLE via the aberrantly phosphorylated STAT3 and STAT4 signaling molecules.
文摘OBJECTIVE: To clone and study the polymorphism within interleukin-4 (IL-4) proximal promoter of asthmatic children. METHODS: The IL-4 proximal promoter segments were amplified and selected by polymerase chain reaction (PCR) and single strand conformation polymorphism (SSCP) with genomic DNA from ten healthy children and forty patients with dominantly allergic familial histories as templates. The selected PCR segments were cloned into recombinant plasmids pIL-4-Jx2. The PCR inserts were sequenced by dideoxy chain termination method. RESULTS: Seven aberrant bands were found in SSCP analysis from forty asthmatic patients. The sequencing results showed that four variant sites were found within or adjacent to the known IL-4 regulatory element. A C to A transversion located at -229 position was just within the positive regulatory element-I (PRE-I) in one patient. A C to T transition adjacent to the negative regulatory element-II (NRE-II) and an extra G adjacent to TATA box were found in two patients. A five base nucleotide deletion was found near signal transducers and activators of transcription-6 responsive element (STAT-6 RE) in one patient. CONCLUSION: There were polymorphisms within the IL-4 proximal promoter of allergic asthmatic patients and these polymorphisms might result in aberrant expression of IL-4 gene and asthma.
文摘Previous studies with deletion and sequence analysis of JDV LTR showed that there is a putative AP-4 responsive element in LTR. By antisense transient assay and gel shifting assay, we for the first time demonstrated that AP-4 modulated JDV gene expression by binding DNA di-rectly to bovine cells. The results, derived from site-directed mutagenesis experiments, suggest that the six base pairs of AP-4 binding site (CAGCTG) have different effects on JDV gene expression. When the first two base pairs changed to GC, JDV gene expression is severely decreased.
