Specificity factor of yeast mitochondrial RNA polymerase. Purification and interaction with core RNA polymerase.

We have identified a mitochondrial protein from Saccharomyces cerevisiae which confers the ability to recognize mitochondrial promoters onto a nonspecifically transcribing mitochondrial core RNA polymerase and we have purified this specificity factor 10,700-fold from a whole cell extract. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified fraction followed by elution and renaturation of protein activity shows that the specificity factor is a 43-kDa polypeptide which directs mitochondrial core RNA polymerase to promoters belonging to rRNA-, tRNA-, and protein-encoding genes, as well as to mitochondrial replication origins. Gel filtration and glycerol gradient sedimentation studies indicate that the specificity factor shows little association with core RNA polymerase in the absence of DNA, and that it behaves like a monomeric 43-kDa protein.

Characterization of the promoter of the large ribosomal RNA gene in yeast mitochondria and separation of mitochondrial RNA polymerase into two different functional components.

We have characterized a DNA sequence that functions in recognition of the promoter of the mitochondrial large rRNA gene by the yeast mtRNA polymerase. Promoter-containing DNA fragments were mutagenized and used as templates to study initiation of transcription in vitro with a partially purified mtRNA polymerase preparation. Deletion mutants, in which increasing stretches of DNA were removed from regions flanking the promoter, define a short area essential for correct initiation of transcription.

Sexual Agglutination in the Unicellular Green Alga Chlamydomonas eugametos: Identification and Properties of the Mating Type plus Agglutination Factor.

Gametes of the unicellular green alga Chlamydomonas eugametos agglutinate via their flagella. The mating type plus agglutination factor was solubilized by relatively mild treatments such as a short pH shock or an osmotic shock indicating that it is an extrinsic membrane component. It was also extracted in the nonionic detergent Triton X-100.