Abstract
Transcriptional regulation of the yeast cytochrome c 1 gene (CYT1) in response to oxygen and carbon source is mediated by Hap1p and the Hap2 complex. Furthermore, the centromere-binding factor 1 (Cbf1p) associates with the CYT1 upstream region (UASCYT1), but its direct activation potential is insignificant. The possible role of Cbf1p as a modulator of transcriptional adaptation to changes in nutritional conditions was examined. In electrophoretic mobility shift assays (EMSA) using yeast nuclear extracts, Cbf1p was found to exist as homo- and heterodimers of processed subforms of 54 and 37 kDa. An additional 18-kDa version was the only species found in anaerobic cells grown under an atmosphere of purified nitrogen, but not when CO2 was used to establish anaerobiosis. All three dimers of the 37 and 54 kDa versions of Cbf1p that occurred in oxidatively growing cells gave rise to hetero-oligomeric complexes containing other as yet unidentified protein(s). Complex formation was not observed with extracts from cultures grown on high levels of glucose and was dependent on pre-assembly in the absence of target DNA. Pre-treatment with alkaline phosphatase enhanced formation of these higher-order complexes. The C-terminal 18-kDa segment of Cbf1p, which can undergo dimerization and bind DNA, does not induce supershifts after preincubation and is not influenced by dephosphorylation. We propose that the N-terminal domain is subject to carbon source- or growth-dependent phosphorylation/dephosphorylation events that result in differential recruitment of additional factors to promoters of genes that encode proteins required for non-fermentative growth.
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Received: 2 July 1998 / Accepted: 14 September 1998
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Oechsner, U., Bandlow, W. Growth-regulated formation of heteromeric complexes of the centromere and promoter factor, Cbf1p, in yeast. Mol Gen Genet 260, 417–425 (1998). https://doi.org/10.1007/s004380050912
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DOI: https://doi.org/10.1007/s004380050912