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Mol. Cell. Biol., Mar 1995, 1698-1708, Vol 15, No. 3
Y Zhu, CL Peterson and MF Christman
The Hpr1 protein has an unknown function, although it contains a region of
homology to DNA topoisomerase I. We have found that hpr1 null mutants are
defective in the transcription of many physiologically unrelated genes,
including GAL1, HO, ADH1, and SUC2, by using a combination of Northern
(RNA) blot analysis, primer extension, and upstream activation
sequence-lacZ fusions. Many of the genes positively regulated by HPR1 also
require SWI1, SWI2-SNF2, SWI3, SNF5, and SNF6. The transcriptional defect
at HO and the CCB::lacZ upstream activation sequence in hpr1 mutants is
partially suppressed by a deletion of SIN1, which encodes an HMG1p-like
protein. Elevated gene dosage of either histones H3 and H4 or H2A and H2B
results in a severe growth defect in combination with an hpr1 null
mutation. However, increased gene dosage of all four histones
simultaneously restores near-normal growth in hpr1 mutants. Altered in vivo
Dam methylase sensitivity is observed at two HPR1-dependent promoters (GAL1
and SUC2). Most of the Hpr1 protein present in the cell is in a large
complex (10(6) Da) that is distinct from the SWI-SNF protein complex. We
propose that HPR1 affects transcription and recombination by altering
chromatin structure.
Copyright © 1995, American Society for Microbiology
HPR1 encodes a global positive regulator of transcription in Saccharomyces cerevisiae
Department of Radiation Oncology, University of California, San Francisco 94143.
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