Abstract #59

The CURI-complex: Potential Link between Production of rRNA and of Ribosomal Proteins? Dipayan Rudra, Jaideep Mallick, Jonathan R. Warner. Dept. of Cell Biology, AECOM, Bronx, NY.
   The 138 genes encoding the 79 ribosomal proteins (RPs) of Saccharomyces cerevisiae form the tightest cluster of coordinately regulated genes in nearly all transcriptome experiments. Ifh1 has been identified as the major transcription factor for the RP genes, to which it is recruited by its interaction with Fhl1, constitutively present almost exclusively at RP genes that are also characterized by pairs of sites for the more general DNA-binding factor, Rap1. The occupancy of the RP genes by Ifh1 depends on its interaction with the phosphopeptide-recognizing Forkhead-Associated (FHA) domain of Fhl1. Investigation of the possible three-way complex between Ifh1, Fhl1, and Rap1 revealed that the major part of the cell’s Ifh1 is, instead, in a different complex, containing CK2, Utp22, and Rrp7, which we have termed the CURI complex. We show that in vitro the CK2 of this complex will phosphorylate Ifh1, but not Rrp7 or Utp22. Whether this phosphorylation site is that necessary for interaction of Ifh1 with the FHA domain of Fhl1 is under investigation. The intriguing feature of the CURI complex is its juxtaposition of the transcription factor, Ifh1, with two of the many proteins involved in early steps of rRNA processing, Utp22 and Rrp7. Since the parallel regulation of rRNA and RP synthesis is well established, the CURI complex may serve as a bridge between rRNA processing and transcription of ribosomal protein genes.

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