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Genetic interaction between TFIIB and SSL2

Shivani Goel
M.S., Biotechnology, 2004
Indian Institute of Technology, Bombay

Thesis Advisor: Michael Hampsey, PhD
Graduate Program in Biochemistry & Molecular Biology

Biochemistry Department Conference Room
RWJMS 6th floor, Research Tower

Thursday, August 12, 2010
9:00 a.m.


Transcription of eukaryotic protein-coding genes is performed by RNA polymerase II. The polymerase requires the action of various transcription factors to carry out this highly regulated process. During transcription initiation, the polymerase along with other general transcription factors forms the pre-initiation complex on promoter DNA. TFIIB is one such general transcription factor and functions in transcription initiation. The yeast TFIIB gene, SUA7 was initially discovered in a genetic screen on the basis of its role in transcription start site selection. More recently it was also shown to function in gene loop formation as defined by the physical juxtaposition of the promoter and terminator region of the gene.
To further understand the role of TFIIB in transcription initiation and gene loop formation, a genetic screen was performed using a sua7 allele defective in start site selection and gene loop formation. One suppressor was identified as an allele of the SSL2 gene which encodes for a subunit of the general transcription factor TFIIH. The suppressor ssl2 allele while having no effect on transcription initiation was able to correct the looping defect. Moreover other known ssl2 alleles also exhibited a looping defect. The genetic interaction between TFIIB and Ssl2 and other ssl2 mutants exhibiting impaired gene loop formation provides us insight into a new role for Ssl2 in gene loop formation. Chromatin immunoprecipitation experiments demonstrate that Ssl2 occupies not only the promoter, but also the terminator region of transcribing genes, similar to the pattern of TFIIB gene occupancy. These results define a function interaction between TFIIB and TFIIH and demonstrate for the first time that the transcription initiation factor TFIIH affects events at both ends of genes transcribed by RNA polymerase II.

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