The largest subunit of RNA polymerase II in Dictyostelium: conservation of the unique tail domain and gene expression.
cDNAs encoding the largest subunit of RNA polymerase II were isolated from a Dictyostelium cDNA library. A total of 2.9 kilobases (kb) of cDNA was sequenced and the amino acid sequence of the carboxyl-terminal half of the protein was deduced. Similar to other eukaryotic RNA polymerases II, the largest subunit of Dictyostelium RNA polymerase II contains a unique repetitive tail domain at its carboxyl-terminal region. It consists of 24 highly conserved heptapeptide repeats, with a consensus sequence of Tyr-Ser-Pro-Thr-Ser-Pro-Ser. In addition to the tail domain, five segments of the deduced primary structure show > 50% sequence identity with either yeast or mouse protein. RNA blots show that cDNA probes hybridized with a single mRNA species of approximately 6 kb and immunoblots using a monoclonal antibody raised against the tail domain lighted up a single protein band of 200 kilodaltons. Interestingly, expression of the largest subunit of RNA polymerase II appears to be under developmental regulation. The accumulation of its mRNA showed a 60% increase during the first 3 h of development, followed by a steady decrease during the next 6 h. Cells began to accumulate a higher level of the RNA polymerase II mRNA after 9 h of development. When cells were treated with low concentrations of cAMP pulses to stimulate the developmental process, the pattern of mRNA accumulation moved 3 h ahead, but otherwise remained similar to that of control cells.
Lam
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Banting and Best Department of Medical Research, University of Toronto, Ont., Canada.
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Yip
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Siu
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D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004023:Dictyostelium / Q000201:enzymology*; D015966:Gene Expression Regulation, Fungal / Q000502:physiology*; D015151:Immunoblotting; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D012319:RNA Polymerase II / Q000737:chemistry* / Q000235:genetics; D017386:Sequence Homology, Amino Acid
D012319:RNA Polymerase II