The phosphoform of the regulatory subunit RII of cyclic AMP-dependent protein kinase possesses intrinsic topoisomerase activity.
The phosphoform of the type II regulatory subunit (phospho-RII-cAMP) of cAMP-dependent protein kinase from rat liver was found to possess intrinsic topoisomerase activity towards several DNA substrates such as phi X174, pBR322, SV40, and M13. Like the type I topoisomerases from several eukaryotic cells, phospho-RII X cAMP can relax both positive and negative superhelical turns of phi X174 DNA. Topological isomers with a decreasing number of superhelical turns can be identified as transient products. Conditions under which phospho-RII X cAMP relaxes superhelical phi X174 DNA lead to transient formation of a DNA-phospho-RII X cAMP complex via DNA strand breakage and covalent attachment of the DNA to a tyrosine residue of phospho-RII X cAMP via a phospho-RII X cAMP depends on the presence of cAMP and is altered by changes in the degree of phosphorylation of RII. Both dephosphorylation and removal of cAMP from phospho-RII X cAMP abolish its topoisomerase activity.
A I
AI
Constantinou
S P
SP
Squinto
R A
RA
Jungmann
D000818:Animals; D010584:Bacteriophage phi X 174; D000242:Cyclic AMP / Q000494:pharmacology*; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004278:DNA, Superhelical / Q000378:metabolism; D004279:DNA, Viral / Q000378:metabolism; D004492:Edetic Acid / Q000494:pharmacology; D007700:Kinetics; D009838:Oligodeoxyribonucleotides / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D004278:DNA, Superhelical; D004279:DNA, Viral; D009838:Oligodeoxyribonucleotides; D019000:Phosphotyrosine; D014443:Tyrosine; D004492:Edetic Acid; D000242:Cyclic AMP; D011494:Protein Kinases; D004264:DNA Topoisomerases, Type I