Non-Histone Proteins Nhp6A and Nhp6B Are Required for the Regulated Expression of SUC2 Gene of Saccharomyces cerevisiae

Abstract

Transcription of the SUC2 gene that encodes invertase enzyme is controlled by glucose repression and derepression mechanisms in Saccharomyces cerevisiae. Several regulatory factors such as Mig1p complex, Gcr1p, Hxk2p, nucleosomes, and the Snf1p kinase complex have been identified as the regulators of SUC2 transcription. The results presented in this study indicate that the non-histone proteins Nhp6A and Nhp6B were also required for the regulated expression of SUC2 gene. Expression of the SUC2 gene reduced to one-fiftieth–one-tenth in the Δnhp6A Δnhp6B double mutant strain depending on the growth conditions. Moreover, SUC2 expression and invertase synthesis became constitutive after long-term derepression, and decreased to a low level in Δnhp6A Δnhp6B double deletion mutant. A time course analysis of the invertase synthesis revealed that both the repression and derepression rates were very slow in the Δnhp6A Δnhp6B double mutant yeast. These results indicate that the architectural transcription factors Nhp6A and Nhp6B play a very critical role in the regulation of SUC2 gene expression.