J Biol Chem 248: 1361-4 (1973)[73097107]
The product of in vitro replication of the ØX174 or M13
viral strand is known to be a circular duplex with a discontinuity in
the synthetic strand (RF II). This replication intermediate has now
been converted to an alkali-stable covalent duplex (RF I) through the
joint action of Escherichia Coli DNA polymerase I and E. coli ligase.
Failure of T4 DNA polymerase to substitute for the E. coli enzyme
implied the presence of an RNA priming segment at the 5' end which
the unique 5' => 3' exonuclease function of the E. coli enzyme can
excise. This suggestion was confirmed by conversion of the RF II
product to an alkali-labile RF I through the joint action of T4 DNA
polymerase and T4 ligase, an enzyme which can join RNA ends, and by
location of the alkali-labile link-age of the RF I in the
complementary (synthetic) strand. These results extend earlier
evidence for RNA priming of DNA replication. They also call attention
to a possible physiological role of E. coli DNA polymerase I in the
excision of such RNA primers during DNA replication.
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