PMID:10559179

Citation	Vaiskunaite, R, Miller, A, Davenport, L and Mosig, G (1999) Two new early bacteriophage T4 genes, repEA and repEB, that are important for DNA replication initiated from origin E. J. Bacteriol. 181:7115-25
Abstract	Two new, small, early bacteriophage T4 genes, repEA and repEB, located within the origin E (oriE) region of T4 DNA replication, affect functioning of this origin. An important and unusual property of the oriE region is that it is transcribed at early and late periods after infection, but in opposite directions (from complementary DNA strands). The early transcripts are mRNAs for RepEA and RepEB proteins, and they can serve as primers for leading-strand DNA synthesis. The late transcripts, which are genuine antisense RNAs for the early transcripts, direct synthesis of virion components. Because the T4 genome contains several origins, and because recombination can bypass a primase requirement for retrograde synthesis, neither defects in a single origin nor primase deficiencies are lethal in T4 (Mosig et al., FEMS Microbiol. Rev. 17:83-98, 1995). Therefore, repEA and repEB were expected and found to be important for T4 DNA replication only when activities of other origins were reduced. To investigate the in vivo roles of the two repE genes, we constructed nonsense mutations in each of them and combined them with the motA mutation sip1 that greatly reduces initiation from other origins. As expected, T4 DNA synthesis and progeny production were severely reduced in the double mutants as compared with the single motA mutant, but early transcription of oriE was reduced neither in the motA nor in the repE mutants. Moreover, residual DNA replication and growth of the double mutants were different at different temperatures, suggesting different functions for repEA and repEB. We surmise that the different structures and protein requirements for functioning of the different origins enhance the flexibility of T4 to adapt to varied growth conditions, and we expect that different origins in other organisms with multiorigin chromosomes might differ in structure and function for similar reasons.
Links	PubMed PMC94188
Keywords	Amino Acid Sequence; Bacteriophage T4/genetics; Bacteriophage T4/metabolism; Base Sequence; DNA Replication/genetics; Genes, Viral/genetics; Molecular Sequence Data; Mutation; Plasmids/genetics; Promoter Regions, Genetic; Replication Origin/genetics; Sequence Analysis, DNA; Viral Proteins/chemistry; Viral Proteins/genetics; Viral Proteins/isolation & purification; Viral Proteins/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
BPT4:REPEA		GO:0090592: DNA synthesis involved in DNA replication	ECO:0000315:		P		repEA is an important gene in DNA synthesis and phage growth of phage T4. However, due to the amalgamation of several initiation sites in the T4 genome, mutations in repEA are not lethal. Nonsense mutations of repEA in conjunction with mot4 (to reduce initiation from different sources) mutations in phages showed smaller plaques compared to phages without both of these mutations (data not shown - from "Nonsense mutations in the repEA and repEB genes in combination with a motA mutation affect phage growth.") The same repEA and mot4 mutation was shown to synthesize much less DNA compared to that of the phage with just the mot4 mutation (Figure 6), which was indicative of the importance of repEA versus other initiator proteins in DNA synthesis.	complete CACAO 13097

References

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