Abstract #41

Gene looping is dependent upon the general transcription factor IIB. Badri N. Singh, Michael Hampsey. Division of Nucleic Acids Research, Department of Biochemistry, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
   The general transcription factor IIB (TFIIB) is required for assembly of the RNA polymerase II (Pol II) transcription preinitiation complex. The Saccharomyces cerevisiae sua7-1 allele encodes an altered form of TFIIB that affects the accuracy of transcription start site selection at a subset of class II genes. The sua7-1 allele also genetically interacts with Ssu72, which is a Pol II CTD phosphatase with specificity for serine-5-P of the CTD. Ssu72 physically binds TFIIB, yet is a component of the CPF 3’-end processing complex. Recently we reported a physical association of promoter and terminator regions of the yeast BUD3 and SEN1 genes resulting in gene loops (Genes Dev. 19:2969 (2005)). These interactions are transcription-dependent and require the Ssu72 and Pta1 components of CPF complex. Here we report that the sua7-1 mutant is defective for loop formation; this defect is not a consequence of impaired transcription, as shown by RT-PCR analysis. Consistent with a role for TFIIB in DNA loops, ChiP experiment shows that TFIIB occupies both the promoter and terminator regions of the affected genes. Furthermore, we have extended our earlier results by demonstrating that gene loops form at the relatively long BLM10 gene, as well as at the shorter genes SAC3 and GAL10. We propose that the gene looping is mediated by physical interaction between CPF and components of the transcription initiation complex and suggest that looping facilitates recycling of RNAPII from the terminator to the promoter during transcription reinitiation.

Return to YGM 2006 Home at SGD