Direction of Translation and Size of Bacteriophage φX174 Cistrons

Abstract

Translation of the bacteriophage φX174 genome follows cistron order D-E-F-G-H-A-B-C. To establish this, the position of a nonsense mutation on the genetic map was compared with the physical size (molecular weight) of the appropriate protein fragment generated in nonpermissive cells. Distances on the φX174 genetic map and distances on a physical map constructed from the molecular weights of φX174 proteins and protein fragments are proportional over most of the genome with the exception of the high recombination region within cistron A.

A high-resolution map of bacteriophage øX174 transcription

“…One main feature of the ϕX174 genome that puzzled and fascinated phage researchers is the presence of extensive gene overlaps. Before the genome was sequenced, it was estimated that more sequence length than is covered by the genome was required to encode the observed expressed proteins (Barrell et al, 1976; Benbow et al, 1972). Sequencing solved this mystery by showing that 8 of the 11 genes in ϕX174 overlap, thereby increasing the available genetic encoding capacity beyond the 5,386 nt genome limit (Barrell et al, 1976; Sanger et al, 1977).…”

Growth and DNA synthesis of bacteriophage phi x174 in a dnaP mutant of Escherichia coli

“…Bacteriophage 4X174 is a small, icosahedral phage containing a single-stranded circular DNA consisting of 5,386 nucleotides and 8 to 10 genes (1,23). Phage multiplication starts with infection.…”

Class of φX174 Mutants Relatively Deficient in Synthesis of Viral RNA

“…The bacteriophage OX174 gene D product, a protein of 14,500 molecular weight, is made in largest molar amount of any OX gene product in infected cells (2,3). The precise function for this protein is not known, however; mutants in gene D do not form progeny single-stranded DNA, but do make a normal amount of double-stranded, replicative-form (RF) DNA (6,8).…”

“…Escherichia coli HF4704 (7) was the nonpermissive host for viral amber mutants, and E. coli HF4714 was the permissive host. Stocks of the gene D mutants used (amlO and am42), obtained from R. M. Benbow, had a reversion frequency of 3 x 10-5 and were prepared as described previously (2). Cells were grown to a density of 5 x 108/ml in 20 ml of TPA medium (13) containing one-tenth the normal phosphate concentration and supplemented with a mixture of 20 natural 1-amino acids (2.7 g/liter) (Nutritional Biochemicals Corp., Cleveland, Ohio) and 10 ,ug of thymine per ml.…”

“…The decrease in the amount of XX mRNA in cells infected with gene D mutants is reflected in a reduction of the amount of virus-specific proteins (2). A decrease in the amount of virus mRNA in cells infected with gene A mutants of the related phage S13 has been observed (11).…”