PROTEIN FACTORS IN BLASTOCLADIELLA-EMERSONII CELL EXTRACTS RECOGNIZE SIMILAR SEQUENCE ELEMENTS IN THE PROMOTERS OF THE GENES ENCODING CAMP-DEPENDENT PROTEIN-KINASE SUBUNITS

Blastocladiella emersonii contains a single cAMP-dependent protein kin ase (PKA), which is similar to the mammalian type II isoforms. Its act ivity is regulated during development by changes in the levels of the catalytic (C) and regulatory (R) subunits, which occur in parallel wit h changes in levels of the corresponding mRNAs, suggesting coordinate transcriptional control of the expression of both subunits. Both R and C mRNA levels are low in vegetative cells, rise sharply during sporul ation and decrease to basal levels again after germination. To investi gate sequence elements common to both Blastocladiella R and C gene pro moters, which might be involved in the coordinate regulation of these genes, their 5'-flanking regions were analyzed by gel mobility shift a nd DNase I footprinting assays. We determined that different DNA-prote in complexes are generated when fragments of the R and C gene promoter s are incubated with extracts from cells expressing (sporulating cells ) or not expressing (vegetative cells) both subunits, and competition experiments suggested that similar proteinfactors bind to both promote rs. DNase I footprinting experiments have indicated that a sequence co mmon to both R and C promoters, and similar to mammalian E-boxes, bind s factors present in extracts from vegetative and sporulating cells, w hereas sequences flanking the E-boxes in both promoters showed a chang e in the pattern of DNase I digestion only when the vegetative cell ex tract was used. This result suggests that the composition of the prote in complexes binding to these regions changes during sporulation.