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Neuronal Insulin Receptor Substrate (IRS)-2 Expression is Regulated by ZBP89 ... Related Articles

Neuronal Insulin Receptor Substrate (IRS)-2 Expression is Regulated by ZBP89 and SP1 Binding to the IRS-2 Promoter.

J Endocrinol. 2009 Oct 29;

Authors: Udelhoven M, Pasieka M, Leeser U, Krone W, Schubert M

Since neuronal IRS-2 mediated signals coordinate key processes in rodent physiology like food intake, fertility, longevity, as well as aging related behaviour we analyzed mechanisms of neuronal IRS-2 expression in neuroblastoma (SHSY5Y) and hypothalamic (GT1-7) cell lines. Using dual luciferase reporter assays and IRS-2 promoter deletion constructs we identified a regulatory cassette within the IRS-2 promoter between -779 bp and -679 bp from the translational start which is responsible for ~50 % of neuronal IRS-2 promoter activity. ChIP assays and EMSA revealed four overlapping ZBP89/SP1 binding sites which alternatively bind ZBP89 or SP1. Activation of this cassette is inhibited by PI3K via increased ZBP89 binding to the promoter. Serum starvation caused increased SP1 binding at one specific SP1 site and decreased binding to another proving a regulatory interaction between the different binding sites within this promoter cassette to tightly control IRS-2 expression. Mutants containing all possible combinations of one, two, three or all four SP1 binding sites of the IRS-2 promoter revealed that SP1 binding to one particular site is most important for promoter activation. Stable downregulation of ZBP89 using siRNA substantially increased IRS-2 mRNA and protein expression. Thus, alternative binding of ZBP89 or SP1 to the described region in the IRS-2 promoter regulates neuronal IRS-2 expression in a PI3K dependant manner.

PMID: 19875459 [PubMed - as supplied by publisher]

Transcriptional activation of pref-1 by E2F1 in 3T3 L1 cells.

BMB Rep. 2009 Oct 31;42(10):691-6

Authors: Shen YN, Kim YM, Yun CH, Moon YS, Kim SH

The E2F gene family appears to regulate the proliferation and differentiation of events that are required for adipogenesis. Pref-1 is a transmembrane protein that inhibits adipocyte differentiation in 3T3-L1 cells. In this study, we found that the expression of pref-1 is regulated by the transcription factor E2F1. The expression of pref-1 and E2F1 was strongly induced in preadipocytes and at the late differentiation stage. Using luciferase reporter assay, ChIP assay and EMSA, we found that the -211/-194 region of the pref-1 promoter is essential for the binding of E2F1 as well as E2F1-dependent transcriptional activation. Knockdown of E2F1 reduced both pref-1 promoter activity and the level of pref-1 mRNA. Taken together, our data suggest that transcriptional activation of pref-1 is stimulated by E2F1 protein in adipocytes. [BMB reports 2009; 42(10): 691-696].

PMID: 19874716 [PubMed - in process]