Complete nucleotide sequence of the bacteriophage λ DNA region containing gene Q and promoter pR

It is well known now that the main regulation stages of bacteriophage X development occur on the level of transcription. The regulation of transcription does not occur only at the initiation stage but also at the termination stage. It has been shown that at the early steps of phage )t development the regulation of termination is controlled by phage-specific protein, product ofgeneN. This protein provides anti-termination of RNA originating from promoters PL and PR [1-51. At the late stage of the phage ~, development, promoter PR' is used for the effective transcription of the lysis and morphology genes [5-8]. A product of X gene Q is necessary for efficient synthesis of/ate messenger RNA origination from PR' (reviews [5,8]). Protein Q seems not to be an activator of the promoter PR', but to provide elongation of the short 6 S RNA promoted by PR' [6,7,9]. It has been proposed [5,6] that this transcript is a 'leader sequence' for late gene expression, and that protein Q, like protein N, is an anti-terminator protein. Here, we have determined the primary structure of the X DNA fragment between 90.8% and 93.1% of the ~ genome length. This fragment contains gene Q, promoter PR' and gene 6 S RNA with its terminator. MspI, HindIII and TagI were isolated according to [13]. DNA-ligase and polynucleotide kinase were kindly provided by Dr Yu. S. Nechaev and alk',dine phosphatase and DNA polymerase I (Klenov's fragment) by Dr V. G. Korobko. Xci857 DNA was isolated as in [9]. A plasmid DNA was isolated according to [14]. [')'-32p]ATP, [o~-3zpldAYP and [c~-32pIdGTP with spec. act. 2000-3000 Ci/mmol were purchased from Amersham Radiochemical Centre (England). DNA hydrolysis by restriction endonucleases was performed under the conditions in [ 15]. Electrophoresis of the DNA fragments in 1% agarose or 4% polyacrylamide gels and isolation of the fragments from the gels were performed as in [9].