Alpha1-induced DNA bending is required for transcriptional activation by the Mcm1-alpha1 complex.

The yeast Mcm1 protein is a founding member of the MADS-box family of transcription factors that is involved in the regulation of diverse sets of genes through interactions with distinct cofactor proteins. Mcm1 interacts with the Matalpha1 protein to activate the expression of the alpha-cell type-specific genes. To understand the requirement of the cofactor alpha1 for Mcm1-alpha1-dependent transcriptional activation we analyzed the recruitment of Mcm1 to the promoters of alpha-specific genes in vivo and found that Mcm1 is able to bind to the promoters of alpha-specific genes in the absence of alpha1.

Delayed rRNA processing results in significant ribosome biogenesis and functional defects.

mof6-1 was originally isolated as a recessive mutation in Saccharomyces cerevisiae which promoted increased efficiencies of programmed -1 ribosomal frameshifting and rendered cells unable to maintain the killer virus. Here, we demonstrate that mof6-1 is a unique allele of the histone deacetylase RPD3, that the deacetylase function of Rpd3p is required for controlling wild-type levels of frameshifting and virus maintenance, and that the closest human homolog can fully complement these defects. Loss of the Rpd3p-associated histone deacetylase function, either by mutants of rpd3 or loss of the associated gene product Sin3p or Sap30p, results in a delay in rRNA processing rather than in an rRNA transcriptional defect.