Posttranscriptional Regulation of Gene Expression in Epithelial Cells by Polyamines
In addition to regulating gene transcription, polyamines also potently modulate gene expression posttranscriptionally. Posttranscriptional gene regulation, which includes processes such as mRNA transport, turnover, and translation, involves specific mRNA sequences (cis-element) that interact with transacting factors such as RNA-binding proteins (RBPs) and microRNAs. U- or AU-rich elements (ARE) are the best characterized cis-acting sequences located in the 3’-untranslated regions of many labile mRNAs. Several RBPs, including AUF1, BRF1, TTP, and KSRP, promote ARE-mRNA decay through the recruitment of the ARE-bearing mRNA to sites of mRNA degradation, whereas RBPs such as HuR, HuB, HuC, and HuD stabilize target mRNAs and stimulate their translation. HuR is one of the best-studied RBPs and has emerged as a key regulator of posttranscriptional control of gene expression and its activity is tightly regulated by cellular polyamines. Ribonucleoprotein immunoprecipitation assays and biotin pull-down assays are two major methods used extensively in experiments investigating the roles and mechanisms of cellular polyamines in the posttranscriptional regulation and are described in detail in this chapter.
Key wordsRNA-binding proteins, mRNA stability, and translation Posttranscriptional regulation Ribonucleoprotein 3’-Untranslated regions
This work was supported by a Merit Review Grant (to J-Y Wang) from the Department of Veterans Affairs and by NIH Grants DK-57819, DK-61972, DK-68491 (to J-Y Wang). J-Y. Wang is a Research Career Scientist, Medical Research Service, US Department of Veterans Affairs.
- 17.Kramer DJ, Chang BD, Chen Y, Diegelman P, Alm K, Black AR, Roninson IB, Porter CW (2001) Polyamine depletion in human melanoma cells leads to G1 arrest associated with induction of p21WAF1/CIP1/SDI1, changes in the expression of p21-regulated genes, and a senescence-like phenotype. Cancer Res 61:7754–7762PubMedGoogle Scholar
- 21.Patel AR, Li J, Bass BL, Wang JY (1998) Expression of the transforming growthfactor-beta gene during growth inhibition following polyamine depletion. Am J Physiol Cell Physiol 275:C590–C598Google Scholar