The p27Kip1 is a cell cycle repressor protein that regulates primarily the cell cycle transition from G1 to S phase and hence the DNA replication is in the S phase and cell division in the M phase. Expression of p27Ki...The p27Kip1 is a cell cycle repressor protein that regulates primarily the cell cycle transition from G1 to S phase and hence the DNA replication is in the S phase and cell division in the M phase. Expression of p27Kip1 protein has dual roles for both cancer prevention and promotion. For example, numerous nutritional and chemopreventive anti-cancer agents specifically increase the expression of p27Kip1 protein without directly affecting the expression of any other cell cycle regulatory proteins. On the other hand, pro-cancer agents (like glucose, insulin and other growth factors frequently seen in obesity and/or diabetes) specifically decrease the expression of p27Kip1 protein without directly affecting the expression of any other cell cycle regulatory proteins. Unlike expression of any other cell cycle regulatory proteins, expression of p27Kip1 protein is very unusual. The mRNA of p27Kip1 has a very long and unusual 5’-untranslated region (from -575 to -1 in human). It appears that the 5’-untranslated region of p27Kip1 mRNA forms two alternative secondary structures. One increases the expression of p27Kip1 protein when anti-cancer agents are added and another decrease the expression of p27K1p1 when pro-cancer agents are added. For this short concept proposal, Dr. Albert Einstein’s “visualized thought experiments (German: Gedanken experiment)” were used as a fundamental tool for understanding how either anti- or pro-cancer agents bring the primary structure of the 5’-untranslated region of p27Kip1 mRNA into two alternative secondary structures, thereby either increasing or decreasing, respectively, the translation initiation of p27Kip1 protein.展开更多
Full length complementary DNAs (cDNA) are crucial for the functional annotation of genes. Several novel experimental approaches for selective enrichment of full length cDNAs are outlined in parallels. Some kinds of re...Full length complementary DNAs (cDNA) are crucial for the functional annotation of genes. Several novel experimental approaches for selective enrichment of full length cDNAs are outlined in parallels. Some kinds of reverse transcriptases and high fidelity PCR enzymes are introduced for promising high efficiency of accurate full length cDNA synthesis. The temperature profiles of the reverse transcription and PCR are also discussed.展开更多
The efficient translation of most eukaryotic mRNAs requires an interaction between the 5' m7GTP cap structure of mRNA and eIF-4F which is composed of 25-(eIF 4E),46-(eIF-4A), and 220-kDa (p220) subunits. eIF-4E bi...The efficient translation of most eukaryotic mRNAs requires an interaction between the 5' m7GTP cap structure of mRNA and eIF-4F which is composed of 25-(eIF 4E),46-(eIF-4A), and 220-kDa (p220) subunits. eIF-4E binds specifically to the mRNA cap. Evidence indicates that stimulation of eIF-4E phosphorylation increases the efficiency of the translational initiation by an as yet undefined mechanism. Phosphorylation of both eIF-4E and p220 in intact cells is stimulated by growth factors, and eIF-4E phosphorylation appears to be a critical event during cell growth regulation. To date only serine phosphorylation of eIF-4E has been described in vivo. In these studies we found that treatment of HepG2 cells with okadaic acid resulted in eIF-4E phosphorylation on both serine and threonine residues and that tryptic phosphopeptide maps showed several previously unrecognized phosphopeptides. Analysis of p,,' from control and okadaic acid--treated cells dmonstrated serine and threonine phosphorylation under both conditions. The most notable finding was that hyperphosphorylation of eIF-4E and p220 increased binding of p220 but not eIF-4E to the m7GTP.cap structure. we suggest that phosphorylation of eIF-4E is more complicated than previously recognizes and that hyperphosphorylation of eIF-4E and p220recruits more p220 into the protein complex that associate with mRNA caps.展开更多
Research Aims: Obesity and type 2 diabetes are known to be associated with increased risk of various types of cancer. However, the molecular biological mechanism of how the risk of cancer is increased in obesity or ty...Research Aims: Obesity and type 2 diabetes are known to be associated with increased risk of various types of cancer. However, the molecular biological mechanism of how the risk of cancer is increased in obesity or type 2 diabetes is not known. The aim this research is to investigate if the decreased expression of p27Kip1, a cell cycle repressor protein, plays a central role in this mechanism. Research Methods, Previous Studies and Theoretical Backgrounds: It is well known that the expression of p27Kip1 is increased by numerous nutritional or chemopreventive anti-cancer agents. But it has never been known that the expression of p27Kip1 could be decreased, rather than increased, and the risk of cancer could be increased, rather than decreased. This problem was solved recently and this new analytical method was used in this study. Results: 1) The expression of p27Kip1 was indeed significantly decreased in human obese type 2 diabetic individuals relative to the lean normal controls. 2) The expression of p27Kip1 was also significantly decreased in genetically obese rodents relative to the lean normal controls. Additionally, in obese rodents, the concentrations of glucose or insulin were significantly increased relative to the lean normal controls. 3) Using human cells cultured in vitro it was found that the increased concentrations of glucose or insulin decrease the expression of p27Kip1. Conclusions: These results suggest that higher concentrations of glucose or insulin increase the risk of various types of cancer in obesity or type 2 diabetes by decreasing the expression of p27Kip1.展开更多
All eukaryotic mRNAs are capped at their 5＇ end. Capping of mRNAs takes place co-transcriptionally and involves three steps. The intermediates of the capping process, as well as the uncapped 5＇ tri-phosphate RNA, ar...All eukaryotic mRNAs are capped at their 5＇ end. Capping of mRNAs takes place co-transcriptionally and involves three steps. The intermediates of the capping process, as well as the uncapped 5＇ tri-phosphate RNA, are resistant to decapping and degradation by known factors, leading to the assumption that the capping process always proceeds to completion. This view was recently drastically changed. A novel family of enzymes, including the yeast proteins Rail, Dxo1/Ydr370C, and the mammalian protein DXO/Dom3Z, has been identified. These enzymes catalyze the conversion of the improperly capped mRNAs to 5＇ mono-phosphate RNA, allowing them to be degraded by 5＇-3＇ exoribonucleases. Several of these enzymes also possess 5＇-3＇ exoribonuclease activities themselves, and can single-handedly clear the improperly capped mRNAs. Studying of these enzymes has led to the realization that mRNA capping does not always proceed to completion, and the identification of an mRNA capping quality control mechanism in eukaryotes. In this paper, we briefly review recent advances in this area.展开更多
文摘The p27Kip1 is a cell cycle repressor protein that regulates primarily the cell cycle transition from G1 to S phase and hence the DNA replication is in the S phase and cell division in the M phase. Expression of p27Kip1 protein has dual roles for both cancer prevention and promotion. For example, numerous nutritional and chemopreventive anti-cancer agents specifically increase the expression of p27Kip1 protein without directly affecting the expression of any other cell cycle regulatory proteins. On the other hand, pro-cancer agents (like glucose, insulin and other growth factors frequently seen in obesity and/or diabetes) specifically decrease the expression of p27Kip1 protein without directly affecting the expression of any other cell cycle regulatory proteins. Unlike expression of any other cell cycle regulatory proteins, expression of p27Kip1 protein is very unusual. The mRNA of p27Kip1 has a very long and unusual 5’-untranslated region (from -575 to -1 in human). It appears that the 5’-untranslated region of p27Kip1 mRNA forms two alternative secondary structures. One increases the expression of p27Kip1 protein when anti-cancer agents are added and another decrease the expression of p27K1p1 when pro-cancer agents are added. For this short concept proposal, Dr. Albert Einstein’s “visualized thought experiments (German: Gedanken experiment)” were used as a fundamental tool for understanding how either anti- or pro-cancer agents bring the primary structure of the 5’-untranslated region of p27Kip1 mRNA into two alternative secondary structures, thereby either increasing or decreasing, respectively, the translation initiation of p27Kip1 protein.
文摘Full length complementary DNAs (cDNA) are crucial for the functional annotation of genes. Several novel experimental approaches for selective enrichment of full length cDNAs are outlined in parallels. Some kinds of reverse transcriptases and high fidelity PCR enzymes are introduced for promising high efficiency of accurate full length cDNA synthesis. The temperature profiles of the reverse transcription and PCR are also discussed.
文摘The efficient translation of most eukaryotic mRNAs requires an interaction between the 5' m7GTP cap structure of mRNA and eIF-4F which is composed of 25-(eIF 4E),46-(eIF-4A), and 220-kDa (p220) subunits. eIF-4E binds specifically to the mRNA cap. Evidence indicates that stimulation of eIF-4E phosphorylation increases the efficiency of the translational initiation by an as yet undefined mechanism. Phosphorylation of both eIF-4E and p220 in intact cells is stimulated by growth factors, and eIF-4E phosphorylation appears to be a critical event during cell growth regulation. To date only serine phosphorylation of eIF-4E has been described in vivo. In these studies we found that treatment of HepG2 cells with okadaic acid resulted in eIF-4E phosphorylation on both serine and threonine residues and that tryptic phosphopeptide maps showed several previously unrecognized phosphopeptides. Analysis of p,,' from control and okadaic acid--treated cells dmonstrated serine and threonine phosphorylation under both conditions. The most notable finding was that hyperphosphorylation of eIF-4E and p220 increased binding of p220 but not eIF-4E to the m7GTP.cap structure. we suggest that phosphorylation of eIF-4E is more complicated than previously recognizes and that hyperphosphorylation of eIF-4E and p220recruits more p220 into the protein complex that associate with mRNA caps.
文摘Research Aims: Obesity and type 2 diabetes are known to be associated with increased risk of various types of cancer. However, the molecular biological mechanism of how the risk of cancer is increased in obesity or type 2 diabetes is not known. The aim this research is to investigate if the decreased expression of p27Kip1, a cell cycle repressor protein, plays a central role in this mechanism. Research Methods, Previous Studies and Theoretical Backgrounds: It is well known that the expression of p27Kip1 is increased by numerous nutritional or chemopreventive anti-cancer agents. But it has never been known that the expression of p27Kip1 could be decreased, rather than increased, and the risk of cancer could be increased, rather than decreased. This problem was solved recently and this new analytical method was used in this study. Results: 1) The expression of p27Kip1 was indeed significantly decreased in human obese type 2 diabetic individuals relative to the lean normal controls. 2) The expression of p27Kip1 was also significantly decreased in genetically obese rodents relative to the lean normal controls. Additionally, in obese rodents, the concentrations of glucose or insulin were significantly increased relative to the lean normal controls. 3) Using human cells cultured in vitro it was found that the increased concentrations of glucose or insulin decrease the expression of p27Kip1. Conclusions: These results suggest that higher concentrations of glucose or insulin increase the risk of various types of cancer in obesity or type 2 diabetes by decreasing the expression of p27Kip1.
基金Project supported by the National Basic Research Program (973) of China (Nos.2011CB910500 and 2010CB912502)the One Hundred Talent Program of the Chinese Academy of Sciences,China
文摘All eukaryotic mRNAs are capped at their 5＇ end. Capping of mRNAs takes place co-transcriptionally and involves three steps. The intermediates of the capping process, as well as the uncapped 5＇ tri-phosphate RNA, are resistant to decapping and degradation by known factors, leading to the assumption that the capping process always proceeds to completion. This view was recently drastically changed. A novel family of enzymes, including the yeast proteins Rail, Dxo1/Ydr370C, and the mammalian protein DXO/Dom3Z, has been identified. These enzymes catalyze the conversion of the improperly capped mRNAs to 5＇ mono-phosphate RNA, allowing them to be degraded by 5＇-3＇ exoribonucleases. Several of these enzymes also possess 5＇-3＇ exoribonuclease activities themselves, and can single-handedly clear the improperly capped mRNAs. Studying of these enzymes has led to the realization that mRNA capping does not always proceed to completion, and the identification of an mRNA capping quality control mechanism in eukaryotes. In this paper, we briefly review recent advances in this area.
