Phosphorylated guanosine derivatives of eukaryotes: Regulation of DNA-dependent RNA polymerases I,II, and III in fungal development

Three phosphorylated guanosine derivatives designated HS-1, HS-2 and HS-3 synthesised during active protein synthesis in the water-mould, $\text{Achlya}$ sp (1969) were shown to regulate the enzymatic activities of nucleoplasmic and nucleolar DNA-dependent RNA polymerases (RNAP-I, II and III) from both $\text{Achlya}$ and another unrelated water-mould, $\text{Blastocladiella emersonii}$. These HS compounds were without effect on $\text{E. coli}$ DNA-dependent RNA polymerase holoenzyme. The most potent of the three compounds was HS-3 which inhibited the activity of all enzymes completely at 100 μg/ml. HS-1, on the other hand, activated maximally at 1 to 10 μg/ml. HS-1 activation (3-fold) was restricted to enzyme III, and it had only partial inhibitory effects on enzymes I and II. The pattern of synthesis of HS-compounds throughout the 20-hour asexual growth cycle of the organism correlated with the detectable levels of the different RNA polymerases of $\text{Achlya}$.