DNA primase activity associated with DNA polymerase alpha from Xenopus laevis ovaries.

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Abstract
One of the 2 forms of DNA polymerase .alpha. from ovaries of the frog X. laevis catalyzed ribonucleoside triphosphate-dependent DNA synthesis on single-stranded circular fd phage DNA templates. DNA synthesis was dependent on ATP and added template. CTP, GTP and UTP stimulated DNA synthesis but were not required and could not substitute for ATP. DNA synthesis was not inhibited by .alpha.-amanitin. Neither poly(dT [deoxythymidylic acid]) nor double-stranded DNA served as template. Analysis of [32P]-dTMP-labeled product by neutral and alkaline agarose gel electrophoresis showed that 0.1-1-kilobase DNA fragments (average size of .apprxeq. 0.25 kilobase) were synthesized. The fragments were not covalently linked to the template. Either [.alpha.-32P]NMP [nucleoside monophosphate], [.gamma.-32P]ATP, or [.gamma.-32P]GTP were incorporated also into the product. Analysis of the product after hydrolysis by KOH, alkaline phosphatase or bacteriophage T4 3'' .fwdarw. 5'' exonuclease showed the presence of a small oligoribonucleotide primer at the 5'' end of the newly synthesized DNA. NTP[nucleoside triphosphate]-dependent DNA-synthesizing activity copurified on 6 columns and cosedimented during glycerol gradient centrifugation with one form of DNA polymerase .alpha. activity but not with the other form. DNA primase activity is evidently associated with 1 of the 2 forms of X. laevis DNA polymerase .alpha.