VIROLOGY
72,
13-22
(1976)
New att Mutants M. J. SHULMAN,’ National
of Phage A
K. MIZUUCHI, Institutes
of Health,
Accepted
AND
Bethesda,
February
M. M. GOTTESMAN Maryland
20014
2,1976
Phage A inserts its chromosome into that of its host Escherichia coli at specific attachment sites (atts). New deletion and point mutants isolated. The point mutants map as if they are in a region common to not be distinguished from att mutants described earlier (Shulman and Effects of the mutations on the physiology of insertion and excision
as a source of single strands which can reanneal, a strand from one utt annealing with the complementary strand from another utt, perhaps thereby facilitating recombination (Shulman and Gottesman, 1973). The four utts recombine with different efficiencies implying that overall the utts have different structures (see, Gottesman and Weisberg, 1971; and Yarmolinsky, 1972; for reviews). These results suggest the model where the nucleotide sequences of four different utts are represented as uttP = POP’; attB = BOB’; attR = POB’; uttL = BOP’, where 0 is the sequence common to the atts and P, P’, B and B’ sequences specific to certain utts (Signer, 1968; Kaiser and Wu, 1968). The utt mutants were isolated as derivatives of the transducing phage A&t2 (see Methods). These mutants were subjected to genetic analysis and to DNA heteroduplex mapping. Some of these mutations have been found to be extensive deletions or insertions. The other mutations, which show no evidence of being insertions or deletions, are assumed to be point mutations. These mutations have the same effect on Int-Xis promoted recombination as do the utt6 and utt24 mutations described earlier (Shulman and Gottesman, 1973).
INTRODUCTION
The temperate bacteriophage A inserts its chromosome into that of its host E. coli by recombination at specific “attachment” sites (c&s) on the phage and bacterial chromosome (Fig. 1). Insertion requires the product of the phage int gene; excision of the phage chromosome requires the products of both the phage int and xis genes. The &t’s (attP, attB, attL, c&R) depicted in Fig. 1 have been examined to see if they have nucleotide sequences in common. The results of such tests indicate that if the atts have a sequence in common, this sequence is too short to visualize by heteroduplex mapping (Hradecna and Szybalski, 1969; Davis and Parkinson, 19’71) or to permit general recombination (
72,
13-22
(1976)
New att Mutants M. J. SHULMAN,’ National
of Phage A
K. MIZUUCHI, Institutes
of Health,
Accepted
AND
Bethesda,
February
M. M. GOTTESMAN Maryland
20014
2,1976
Phage A inserts its chromosome into that of its host Escherichia coli at specific attachment sites (atts). New deletion and point mutants isolated. The point mutants map as if they are in a region common to not be distinguished from att mutants described earlier (Shulman and Effects of the mutations on the physiology of insertion and excision
as a source of single strands which can reanneal, a strand from one utt annealing with the complementary strand from another utt, perhaps thereby facilitating recombination (Shulman and Gottesman, 1973). The four utts recombine with different efficiencies implying that overall the utts have different structures (see, Gottesman and Weisberg, 1971; and Yarmolinsky, 1972; for reviews). These results suggest the model where the nucleotide sequences of four different utts are represented as uttP = POP’; attB = BOB’; attR = POB’; uttL = BOP’, where 0 is the sequence common to the atts and P, P’, B and B’ sequences specific to certain utts (Signer, 1968; Kaiser and Wu, 1968). The utt mutants were isolated as derivatives of the transducing phage A&t2 (see Methods). These mutants were subjected to genetic analysis and to DNA heteroduplex mapping. Some of these mutations have been found to be extensive deletions or insertions. The other mutations, which show no evidence of being insertions or deletions, are assumed to be point mutations. These mutations have the same effect on Int-Xis promoted recombination as do the utt6 and utt24 mutations described earlier (Shulman and Gottesman, 1973).
INTRODUCTION
The temperate bacteriophage A inserts its chromosome into that of its host E. coli by recombination at specific “attachment” sites (c&s) on the phage and bacterial chromosome (Fig. 1). Insertion requires the product of the phage int gene; excision of the phage chromosome requires the products of both the phage int and xis genes. The &t’s (attP, attB, attL, c&R) depicted in Fig. 1 have been examined to see if they have nucleotide sequences in common. The results of such tests indicate that if the atts have a sequence in common, this sequence is too short to visualize by heteroduplex mapping (Hradecna and Szybalski, 1969; Davis and Parkinson, 19’71) or to permit general recombination (
