Cloning and characterization of a novel gene (C17orf25) from the deletion region on chromosome 17p13.3 in hepatocelular carcinoma

Using a combination of hybridization of PAC to a cDNA library and RACE technique, we isolated a novel cDNA, designated as C17orf25 (Chromosome 17 open rea(ling frame 25, previously named it HC71A), from the deletion region on chromosome 17p13.3. The cDNA encodes a protein of 313 amino acids with a calculated molecular mass of 34.8 kDa. C17orf25 is divided into 10 exons and 9 introns, spanning 23 kb of genomic DNA. Northern blot analysis showed that the mRNA expression of C17orf25 was decreased in hepatocellular carcinoma samples as compared to adjacent noncancerous liver tissues from the same patients. The transfection of C17or25 into the hepatocellular carcinoma cell SMMC7721 and overexpression could inhibit the cell growth. The above results indicate that C17orf25 is a novel human gene, and the cloning and preliminary characterization of C17orf25 is a prerequisite for further functional analysis of this novel gene in human hepatocellular carcinoma.

The promoter analysis of the human C17orf25 gene, a novel chromosome 17pl3.3 gene

The human C17orf25 gene (Accession No. AF177342) is one of thirteen genes cloned from a region displaying a high score of loss of heterozygosity within chromosome 17pl3.3 in human hepatocellular carcinoma in China[l]. To unveil the underlying mechanisms for the transcription regulation of this gene and understand its implication to the hepatocellular carcinogenesis, we looked into the relevant aspects by both bioinformatic and experimental executions. We found: 1, The abundant expression of the C17orf25 gene was evident in all the cell lines and tissue samples tested, showing little hepatoma-selectivity; 2, Its transcription starts at a single site, locating at -60 from the translation initiation codon; 3, A 58 bp fragment containing the transcription start, extending from -112 to -55, represents the minimal promoter; 4, The consensus sequence within this fragment recognized by SP1 contributes predominantly to the activity of the minimal promoter; 5, The bioinformatic analysis suggests that the C17orf25 gene may encode a protein in the family of the glyoxalase. Our data has provided some deep insight into both function and regulation of the C1 7orf25 gene in the context of the normal liver and hepatocellular carcinoma.

CHROMOSOME 17P MAY HARBOR MULTIPLE TUMOR SUPPRESSOR GENES ASSOCIATED WITH PRIMARY GLIOBLASTOMA MULTIFORME

Objective: To investigate whether deletion of chromosome 17 is involved in the carcinogenesis of primary glioblastoma multiforme and to localize the possible common deletion region in the aforementioned chromosome. Methods: Polymerase chain reaction-based microsatellite analysis was used to assess loss of heterozygosity (LOH) on chromosome 17 in 20 primary glioblastoma multiforme (GBM). Fifteen fluorescent dye-labeled polymorphic markers were used. Results: Thirteen of twenty (65%) GBM displayed LOH on at least one marker of chromosome 17p. Two tumors showed either LOH or non-informativeness on all markers tested. The most frequent LOH was observed at loci including D17s799 (53.3%), D17s1852 (53.8%), D17s938 (63.20/o), D17s831 (55.6%). The loci D17s831 (on 17p13) and D17s799–D17s1852 (17p11.2–p12) are distal and proximal to p53 respectively. The frequencies of LOH at all loci examined on chromosome 17q were relatively low (<30%). None of informative loci exhibited microsatellite instability in this study. Conclusion: Loss of genetic material on chromosome 17p may play an important role in the pathogenesis of GBM. Besides the well-known TSG p53 on 17p, other unknown TSCs associated with GBM may be present on the chromosomal regions 17p13 and 17p11.2–p12, which are distal and proximal to p53 respectively.

Screening of genetic loci predisposing to herpes simplex virus infection on mouse chromosome 17

Aim:The herpes simplex virus(HSV),one of the most common viruses infecting humans,is featured by a high infection rate and usually causes complex disorders difficult to diagnose and treat.Disease progression is always combined with the specific interaction between organism and environment,but genetic factors play a decisive role in most pathogenic processes.Like most human disorders,individual difference has also been involved in the pathogenesis of HSV infection.The present study aimed to screen the potential gene loci that regulates human predisposition to HSV infection.Methods:With reference to previous studies,inbred mouse lines with significantly distinct predisposition to HSV infection were chosen for gene loci screening.Gene sites on mouse chromosome 17 associated with susceptibility to HSV infection were then identified by correlation analysis and genome-wide scanning technique.Results:Genes affecting the vulnerability of mice to HSV infection were mapped to three regions on the 17th mouse chromosome,D17MIT51.1,D17MIT39.1 and the region between D17MIT180.1 and D17MIT184.Conclusion:The results suggest that the mouse genetic background plays an important role in its susceptibility to HSV-1 infection,which might be regulated by multiple predisposing quantitative trait loci.

The ATF/CREB site is the key element for transcription of the human RNA methyltransferase like1(RNMTL1) gene, a newly discovered 17p13.3 gene

The human RNA methyltransferase like 1 gene (RNMTL1) is one of thirteen newly discovered genes within a 116 Kb segment of the chromosome 17pl3.3 that suffers from a high frequent loss of heterozygosity in human hepatocellular carcinoma in China[1-5]. To understand the molecular mechanisms underlying transcription control of the RNMTL1 gene in human cancers, we decline using of the conventional approach where the cis-elements bound by the known transcription factors are primary targets, and carried out the systematic analyses to dissect the promoter structure and identify/characterize the key cis-elements that are responsible for its strong expression in cell. The molecular approaches applied included 1, the primer extension for mapping of the transcription starts; 2, the transient transfection/reporter assays on a large number of deletion and site-specific mutants of the promoter segment for defining the minimal promoter and the crucial elements within; and 3, the electrophoresis mobility shift assay with specific antibodies for reconfirming the nature of the transcription factors and their cognate cis-elements. We have shown that the interaction of an ATF/CREB element (-38 to -31) and its cognate transcription factors play a predominant role in the promoter activity of the RNMTL1 gene. The secondary DNA structures of the ATF/CREB element play a more vital role in the protein-DNA interaction. Finally, we reported a novel mechanism underlying the YY1 mediated transcription repression, namely, the ATF/CREB dependent transcription-repression by YY1 is executed in absence of its own sequence-specific binding.