Activating transcription factor 4 （ATF4） has been shown to play key roles in many physiological processes. There are no reports, however, demonstrating a direct link between ATF4 and lipid metabolism. We noticed tha...Activating transcription factor 4 （ATF4） has been shown to play key roles in many physiological processes. There are no reports, however, demonstrating a direct link between ATF4 and lipid metabolism. We noticed that Atf4- deficient mice are lean, suggesting a possible role for ATF4 in regulating lipid metabolism. The goal of our current study is to investigate the involvement of ATF4 in lipid metabolism and elucidate the underlying mechanisms. Studies using Atf4-deficient mice revealed increased energy expenditure, as measured by oxygen consumption. These mice also showed increases in lipolysis, expression of uncoupling protein 2 （UCP2） and p-oxidation genes and decreases in expression of lipogenic genes in white adipose tissue （WAT）, suggesting increased utilization and decreased synthesis of fatty acids, respectively. Expression of UCP1, 2 and 3 was also increased in brown adipose tissue （BAT）, suggesting increased thermogenesis. The effect of ATF4 deletion on expression of UCPs in BAT suggests that increased thermogenesis may underlie increased energy expenditure. Thus, our study identifies a possible new function for ATF4 in regulating lipid metabolism and thermogenesis.展开更多
RNA polymerase （Pol） Ⅱ transcription persists in TATA-box-binding protein （TBP）^-/- mutant mouse embryos, indicating TBP-independent mechanisms for Pol Ⅱ transcription in early development. TBP-related factor 3 ...RNA polymerase （Pol） Ⅱ transcription persists in TATA-box-binding protein （TBP）^-/- mutant mouse embryos, indicating TBP-independent mechanisms for Pol Ⅱ transcription in early development. TBP-related factor 3 （TRF3） has been proposed to substitute for TBP in TBP^-/- mouse embryos. We examined the expression of TRF3 in maturing oocytes and early embryos and found that TRF3 was co-expressed with TBP in the meiotic oocytes and early embryos from the late one-cell stage onward. The amounts of TBP and TRF3 changed dynamically and correlated well with transcriptional activity. Chromatin immunoprecipitation （CHIP） assay revealed that different gene promoters in mouse embryonic stem （ES） cells recruited TRF3 and TBP selectively. Comparative analyses of TRF3 and TBP during cell cycle showed that both factors proceeded through cell cycle in a similar pace, except that TRF3 was slightly delayed than TBP in entering the nucleus when cells were exiting the M-phase. Data from expression and biochemical analyses therefore support the hypothesis that TRF3 plays a role in early mouse development. In addition, results from co-localization study suggest that TRF3 may be also involved in Pol Ⅰ transcription.展开更多
The decoding release factor （RF） triggers termination of protein synthesis by functionally mimicking a tRNA to span the decoding centre and the peptidyl transferase centre （PTC） of the ribosome. Structurally, it m...The decoding release factor （RF） triggers termination of protein synthesis by functionally mimicking a tRNA to span the decoding centre and the peptidyl transferase centre （PTC） of the ribosome. Structurally, it must fit into a site crafted for a tRNA and surrounded by five other RNAs, namely the adjacent peptidyl tRNA carrying the completed polypeptide, the mRNA and the three rRNAs. This is achieved by extending a structural domain from the body of the protein that results in a critical conformational change allowing it to contact the PTC. A structural model of the bacterial termination complex with the accommodated RF shows that it makes close contact with the first, second and third bases of the stop codon in the mRNA with two separate loops of structure＂ the anticodon loop and the loop at the tip of helix orS. The anticodon loop also makes contact with the base following the stop codon that is known to strongly influence termination efficiency. It confirms the close contact of domain 3 of the protein with the key RNA structures of the PTC. The mRNA signal for termination includes sequences upstream as well as downstream of the stop codon, and this may reflect structural restrictions for specific combinations of tRNA and RF to be bound onto the ribosome together. An unbiased SELEX approach has been investigated as a tool to identify potential rRNA-binding contacts of the bacterial RF in its different binding conformations within the active centre of the ribosome.展开更多
文摘Activating transcription factor 4 （ATF4） has been shown to play key roles in many physiological processes. There are no reports, however, demonstrating a direct link between ATF4 and lipid metabolism. We noticed that Atf4- deficient mice are lean, suggesting a possible role for ATF4 in regulating lipid metabolism. The goal of our current study is to investigate the involvement of ATF4 in lipid metabolism and elucidate the underlying mechanisms. Studies using Atf4-deficient mice revealed increased energy expenditure, as measured by oxygen consumption. These mice also showed increases in lipolysis, expression of uncoupling protein 2 （UCP2） and p-oxidation genes and decreases in expression of lipogenic genes in white adipose tissue （WAT）, suggesting increased utilization and decreased synthesis of fatty acids, respectively. Expression of UCP1, 2 and 3 was also increased in brown adipose tissue （BAT）, suggesting increased thermogenesis. The effect of ATF4 deletion on expression of UCPs in BAT suggests that increased thermogenesis may underlie increased energy expenditure. Thus, our study identifies a possible new function for ATF4 in regulating lipid metabolism and thermogenesis.
基金This study was supported by grants from National Basic Research Program of China （973 Program） （Nos. 001CB509903 and 001CB509904）Hi-Tech Research and Development Program of China （863 Program） （Nos. 2001AA216121 and 2004AA205010）+3 种基金 National Natural Science Foundation of China （No. 30040003） Science and Technology Committee of Shanghai Municipality （Nos. 99DJ14002, 00DJ1 4033, 01DJ14003, and 03DJ14017） Chinese Academy of Science （No. KSCX-2-3-08）Shanghai Municipal Education Commission and Shanghai Jiao Tong University, School of Medicine.
文摘RNA polymerase （Pol） Ⅱ transcription persists in TATA-box-binding protein （TBP）^-/- mutant mouse embryos, indicating TBP-independent mechanisms for Pol Ⅱ transcription in early development. TBP-related factor 3 （TRF3） has been proposed to substitute for TBP in TBP^-/- mouse embryos. We examined the expression of TRF3 in maturing oocytes and early embryos and found that TRF3 was co-expressed with TBP in the meiotic oocytes and early embryos from the late one-cell stage onward. The amounts of TBP and TRF3 changed dynamically and correlated well with transcriptional activity. Chromatin immunoprecipitation （CHIP） assay revealed that different gene promoters in mouse embryonic stem （ES） cells recruited TRF3 and TBP selectively. Comparative analyses of TRF3 and TBP during cell cycle showed that both factors proceeded through cell cycle in a similar pace, except that TRF3 was slightly delayed than TBP in entering the nucleus when cells were exiting the M-phase. Data from expression and biochemical analyses therefore support the hypothesis that TRF3 plays a role in early mouse development. In addition, results from co-localization study suggest that TRF3 may be also involved in Pol Ⅰ transcription.
文摘The decoding release factor （RF） triggers termination of protein synthesis by functionally mimicking a tRNA to span the decoding centre and the peptidyl transferase centre （PTC） of the ribosome. Structurally, it must fit into a site crafted for a tRNA and surrounded by five other RNAs, namely the adjacent peptidyl tRNA carrying the completed polypeptide, the mRNA and the three rRNAs. This is achieved by extending a structural domain from the body of the protein that results in a critical conformational change allowing it to contact the PTC. A structural model of the bacterial termination complex with the accommodated RF shows that it makes close contact with the first, second and third bases of the stop codon in the mRNA with two separate loops of structure＂ the anticodon loop and the loop at the tip of helix orS. The anticodon loop also makes contact with the base following the stop codon that is known to strongly influence termination efficiency. It confirms the close contact of domain 3 of the protein with the key RNA structures of the PTC. The mRNA signal for termination includes sequences upstream as well as downstream of the stop codon, and this may reflect structural restrictions for specific combinations of tRNA and RF to be bound onto the ribosome together. An unbiased SELEX approach has been investigated as a tool to identify potential rRNA-binding contacts of the bacterial RF in its different binding conformations within the active centre of the ribosome.
