T4 Bacteriophage-coded RNA polymerase subunit blocks host transcription and unfolds the host chromosome

Abstract

T4 bacteriophage mutants selected for their ability to grow with cytosine in their DNA are defective in host transcriptional shutoff and host chromosome unfolding. The host RNA polymerase purifed from cells infected by such a mutant lacks a small T4-coded subunit.

Molecular proof that bacteriophage T4 alc and unf genes are the same gene

“…Thus, we conclude that alc is a nonessential gene. Furthermore, the observation that AlcLJ7 is Unf-is consistent with the conclusion that only those alc mutations which completely inactivate the gene product are measurably Unf deficient (13).…”

“…In particular, we were interested in the Alc2 mutant which, from this work, has a missense mutation and which is phenotypically Unf (13). Both the original Alc2 mutant and the Alc2 MR derivative were Unf- (Fig.…”

“…The Unfoldase assays. The unfoldase assay method was adapted from a published procedure (20) and has been described elsewhere (13). The viscosity was estimated as the time, in seconds, for a 1-ml solution to flow through a 20-gauge needle about 4 cm long.…”

Sequence and cloning of bacteriophage T4 gene 63 encoding RNA ligase and tail fibre attachment activities.

“…A strong T4 'early' promoter recognised by RNA polymerase in vitro maps in this region (H.Gram and W.Ruger, personal communication). The gene is a/c (E.Kutter, R.Drivdahl and K.Rand, in preparation) whose product in some way causes the blocking of host transcription and the unfolding of the host chromosome (Sirotkin et al, 1977). Efficient promoters can interfere with plasmid replication (Stueber and Bujard, 1982) and it is well known that strong promoters are difficult to clone.…”

“…Our limited data are consistent with the second possibility; we have been unable to isolate clones which contain both the 5' end of this gene and the T4 promoter, or clones containing the 5' end orientated such that its expression could occur via the lac promoter of M13mp8 (see Figure 3). The gene is a/c (E.Kutter, R.Drivdahl and K.Rand, in preparation) whose product in some way causes the blocking of host transcription and the unfolding of the host chromosome (Sirotkin et al, 1977). It should not be surprising, therefore, to be unable to isolate any clone in which alc is expressed.…”