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Primer initiation and extension by T7 DNA primase
Author(s) -
Qimron Udi,
Lee SeungJoo,
Hamdan Samir M,
Richardson Charles C
Publication year - 2006
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/sj.emboj.7601112
Subject(s) - biology , primase , primer (cosmetics) , genetics , primer extension , extension (predicate logic) , dna , microbiology and biotechnology , base sequence , polymerase chain reaction , programming language , gene , reverse transcriptase , chemistry , organic chemistry , computer science
T7 DNA primase is composed of a catalytic RNA polymerase domain (RPD) and a zinc‐binding domain (ZBD) connected by an unstructured linker. The two domains are required to initiate the synthesis of the diribonucleotide pppAC and its extension into a functional primer pppACCC ( de novo synthesis), as well as for the extension of exogenous AC diribonucleotides into an ACCC primer (extension synthesis). To explore the mechanism underlying the RPD and ZBD interactions, we have changed the length of the linker between them. Wild‐type T7 DNA primase is 10‐fold superior in de novo synthesis compared to T7 DNA primase having a shorter linker. However, the primase having the shorter linker exhibits a two‐fold enhancement in its extension synthesis. T7 DNA primase does not catalyze extension synthesis by a ZBD of one subunit acting on a RPD of an adjacent subunit ( trans mode), whereas de novo synthesis is feasible in this mode. We propose a mechanism for primer initiation and extension based on these findings.