title: A newly detected class of mammalian single strand-specific DNA-binding proteins. Effects on DNA polymerase alpha-catalyzed DNA synthesis.
abstract: Using a rapid purification scheme, we have isolated from calf thymus cells two single strand-specific DNA-binding proteins, with apparent molecular masses of 48 and 61 kDa. These proteins remained undetected in earlier studies on DNA-binding proteins from calf thymus because they are extremely sensitive to proteolytic breakdown occurring during purification. The proteins are immunologically and biochemically related. They also share a number of functional properties. Both proteins bind noncooperatively to single-stranded DNA and almost totally ignore double-stranded DNA. Both proteins stimulate DNA synthesis catalyzed by mammalian DNA polymerase alpha in the presence of an excess of "activated" DNA as primer-template. The stimulation factor was between 2 and 100 depending on the protein/DNA ratio. We have analyzed this effect in more detail with specifically primed single-stranded phage fd DNA as template and concluded that the proteins block nonproductive polymerase-binding sites on single-stranded DNA sequences, thereby increasing the probability for an association of polymerase with 3'-OH primer ends.
mesh_terms: D000818:Animals; D001435:Bacteriophages; D002417:Cattle; D004247:DNA / Q000096:biosynthesis*; D004257:DNA Polymerase II / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000378:metabolism; D004279:DNA, Viral; D004268:DNA-Binding Proteins / Q000302:isolation & purification / Q000494:pharmacology / Q000502:physiology*; D009693:Nucleic Acid Hybridization; D013698:Templates, Genetic; D013950:Thymus Gland / Q000032:analysis
chemical_list: D004277:DNA, Single-Stranded; D004279:DNA, Viral; D004268:DNA-Binding Proteins; D004247:DNA; D004257:DNA Polymerase II