Hormonal regulation of mRNA stability and RNA-protein interactions in the pituitary

Regulating gene expression from DNA to protein is a complex multistage proc ess with multiple control mechanisms. Transcriptional regulation has been c onsidered the major control point of protein production in eukaryotic cells ; however, there is growing evidence of pivotal posttranscriptional regulat ion for many genes. This has prompted extensive investigations to elucidate the mechanisms controlling RNA processing, mRNA nuclear export and localiz ation, mRNA stability and turnover, in addition to translational rates and posttranslational events. The regulation of mRNA stability has emerged as a critical control step in determining the cellular mRNA level, with individ ual mRNAs displaying a wide range of stability that has been linked to disc rete sequence elements and specific RNA-protein interactions. This review w ill focus on current knowledge of the determinants of mRNA stability and RN A-protein interactions in the pituitary. This field is rapidly expanding wi th the identification of regulated cis-acting stability-modifying elements within many mRNAs, and the cloning and characterization of trans-acting pro teins that specifically bind to their cognate cis elements. We will present evidence for regulation of multiple pituitary genes at the level of mRNA s tability and some examples of the emerging data characterizing RNA-protein interactions.