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Evolutionary complementation for polymerase II CTD function
Author(s) -
Stiller John W.,
Mcconaughy Betty L.,
Hall Benjamin D.
Publication year - 2000
Publication title -
yeast
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.923
H-Index - 102
eISSN - 1097-0061
pISSN - 0749-503X
DOI - 10.1002/(sici)1097-0061(20000115)16:1<57::aid-yea509>3.0.co;2-e
Subject(s) - ctd , biology , rna polymerase ii , genetics , gene , transcription (linguistics) , complementation , conserved sequence , protein subunit , mutant , gene expression , promoter , peptide sequence , linguistics , oceanography , philosophy , geology
The C‐terminal domain (CTD) of the largest subunit (RPB1) of eukaryotic RNA polymerase II is essential for pol II function and has been shown to play a number of important roles in the mRNA transcription cycle. The CTD is composed of a tandemly repeated heptapeptide that is conserved in yeast, animals, plants and several protistan organisms. Some eukaryotes, however, have what appear to be degenerate or deviant CTD regions, and others have no CTD at all. The functional and evolutionary implications of this variation among RPB1 C‐termini is largely unexplored. We have transformed yeast cells with a construct consisting of the yeast RPB1 gene with 25 heptads from the primitive protist Mastigamoeba invertens in place of the wild‐type CTD. The Mastigamoeba heptads differ from the canonical CTD by the invariable presence of alanines in place of threonines at position 4, and in place of serines at position 7 of each heptad. Despite this double substitution, mutants are viable even under conditions of temperature and nutrient stress. These results provide new insights into the relative functional importance of several of the conserved CTD residues, and indicate that in vivo expression of evolutionary variants in yeast can provide important clues for understanding the origin, evolution and function of the pol II CTD. Copyright © 2000 John Wiley & Sons, Ltd.