Transcription and mRNA processing are regulated by phosphorylation and dephosphorylation of the carboxyl-terminal domain (CTD) of RNA polymerase II, which consists of tandem repeats of a YSPTSPS heptapeptide. Previous studies showed that members of the plant CPL (CTD phosphatase-like) protein family differentially regulate osmotic-stress- and ABA-responsive transcription in Arabidopsis thaliana. Among the CPL genes identified in the Arabidopsis genome, CPL1 and CPL2 represent a novel CTD phosphatase, which exhibits unique position specificity for phosphorylated Ser 5 in the CTD repeat, and contains double-stranded RNA binding domains. This project aims to identify the molecular network that regulates stress-responsive transcription through CTD phosphorylation. The in vivo function of each domain of CPL1 will be determined by expressing mutagenized CPL1 in a CPL1 null mutant strain (fry2-1). Proteins interacting with CPL1 (CIF: CPL-interacting factor) will be identified using the yeast two-hybrid system, and will be further characterized by testing genetic interactions of cpl and cif mutant alleles. Functionality of CPL-CIF interaction during stress response will be analyzed by testing physiological stress responses, as well by analyzing stress-inducible transcriptional activation. Through the project, junior scientists (postdocs, graduate/undergraduate students) will be trained for integrated studies of core transcriptional machinery using molecular genetic and biochemical strategies. The data/materials/mutants generated by the project will be deposited in the public domain as they become available.
