Biomedical subjects

C A Keleher

Publications and source records attributed to C A Keleher.

3 recordsLinked to original sources

PubMed1992

Ssn6-Tup1 is a general repressor of transcription in yeast.

The homeodomain protein alpha 2 and the SRF-like protein Mcm1 are required to establish cell type in the yeast Saccharomyces cerevisiae. Together, these regulatory proteins recognize a specific DNA operator, marking a set of genes for transcriptional repression. In this paper, we show that occupancy of the operator by alpha 2-Mcm1 is not sufficient to bring about repression. Rather, repression is effected only when Ssn6 (a TPR protein) and Tup1 (a beta-transducin repeat protein) are also present in the cell. We show that Ssn6 represses transcription when brought to a promoter by a bacterial DNA-binding domain and that Tup1 is required for this repression. Based on these and other results, we propose that Ssn6-Tup1 is a general repressor of transcription in yeast, recruited to target promoters by a variety of sequence-specific DNA-binding proteins.

Immunoblotting↗

PubMed1989

Yeast repressor alpha 2 binds to its operator cooperatively with yeast protein Mcm1.

To bring about repression of a family fo genes in Saccharomyces cerevisiae called the a-specific genes, two transcriptional regulatory proteins, alpha 2 and GRM (general regulator of matin type), bind cooperatively to an operator found upstream of each a-specific gene. To date, GRM has been defined only biochemically. In this communication we show that the product of a single yeast gene (MCM1) is sufficient to bind cooperatively with alpha 2 to the operator. We also show that antiserum raised against the MCM1 gene product recognizes GRM from yeast cells. These results, in combination with previous observations, provide strong evidence that MCM1 encodes the GRM activity.

Electrophoresis, Polyacrylamide Gel↗

PubMed1988

The yeast cell-type-specific repressor alpha 2 acts cooperatively with a non-cell-type-specific protein.

The yeast alpha 2 protein is a cell-type-specific transcriptional repressor. It acts by binding to an operator located upstream of each of its target genes. In this paper, we describe a protein (GRM) that is present in all cell types and binds cooperatively with alpha 2 resulting in an unusual arrangement of the two proteins at the operator. A dimer of alpha 2 occupies the two ends of the operator and straddles the GRM protein, which binds to the center of the operator. Using mutant operators, we show that the recognition sequences for both GRM and alpha 2 are required for repression of a test promoter in vivo. Finally, we deduce that the GRM/alpha 2 cooperativity is mediated through a protein-protein interaction between GRM and the N-terminal domain of alpha 2. This conclusion follows from the observation that the isolated C-terminal domain of alpha 2 can co-occupy the operator with GRM but does not bind cooperatively with GRM.

Base Sequence↗