期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1981
卷号：78
期号：1
页码：205-209
DOI：10.1073/pnas.78.1.205
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The gene 4 protein of bacteriophage T7 recognizes specific sequences on single-stranded DNA and then catalyzes the synthesis of tetraribonucleotide primers complementary to the template. With phi X174 DNA as a template, the gene 4 protein enables T7 DNA polymerase (deoxynucleosidetriphosphate:DNA deoxynucleotidyltransferase, EC 2.7.7.7 ) to initiate DNA synthesis at 13 major sites. DNA sequence analysis of the 5' termini of the newly synthesized DNA shows the predominant recognition sequences for the gene 4 protein to be 3'-C-T-G-G-G-5' or 3'-C-T-G-G-T-5'; the products of synthesis at these sites are RNA primers having the sequences pppA-C-C-C or pppA-C-C-A. The gene 4 protein can also synthesize primers at the sequences 3'-C-T-G-G-AC-5' and 3'-C-T-G-T-N-5', although these sites are used less than 10% as frequently as the predominant sites. Comparison of the utilization of primer sites suggests that the gene 4 protein binds randomly to single-stranded DNA and then translocates along the DNA in a unidirectional 5'-to-3' direction with regard to the DNA strand in search of recognition sequences. Models are presented for the role of the gene 4 protein in the initiation of lagging-strand synthesis and in the initiation of DNA replication at the origin.
