Coupling with Packaging Explains Apparent Recombination of Bacteriophage Lambda by Reca and Recbc Functions Nonreciprocality

نویسنده

  • FRANKLIN W. STAHL
چکیده

Chi (x, 5'-GCTGGTGG) is a recombinator in RecAand RecBC-mediated recombination in Escherichia coli. In vegetative recombination between two bacteriophage lambda strains, one with and the other without Chi (a+x+bX u-Xob+), the X-containing recombinant (a-X+b-) is less abundant than the nonx-containing recombinant (a+xob+). Previously this was taken was evidence for nonreciprocality of X-stimulated exchange. This inequality, however, is now seen to result from an event at cos (X's packaging origin) that both activates Chi and initiates DNA packaging. An event at rightward cos leads to activation of leftward x on the same chromosome for an exchange to its left. From the resulting circulating dimer (-cos-a+-X"-b+-cos-a--x+-b--), the cos that activated x is more likely to be used for rightward packaging initiation than is the cos from the other parent. Consistent with this coupling model is "biased packaging" in X carrying two cos sites per monomer genome. When their maturation is dependent on dimerization by X-stimulated exchange, the phage particles result more often from packaging from the cos that activates x than from packaging from the other cos. Since Chi activation and packaging can be uncoupled, we infer that some early and reversible step in packaging activates x. A strong candidate for this step is a double-strand break at cos that provides an oriented entry site for a recombinase. OLARITY in gene conversion implies special sites on DNA (recombinators) P that locally enhance homologous genetic recombination (LISSOUBA et al. 1962; MURRAY 1963; see STAHL 1979a,b for review). Chi is a special site for the RecBC pathway of recombination in Escherichia coli (for reviews see STAHL 1979a,b; SMITH 1983). When Chi stimulates recombination on bacteriophage lambda, the stimulated crossovers are located primarily to the left of the Chi on the lambda genetic map (leftuard bias) (Figure la) (STAHL and STAHL 1975; STAHL et al. 1980). By inverting DNA segments carrying Chi, FAULDS et al. (1979) and YAGIL et al. (1980) showed that only one orientation of Chi had ' Present address: University of Tokyo Faculty of Medicine, Department of Bacteriology, Hongo 7-3-1, Tokyo-1 13, Japan. Genetics 108: 773-794 December, 1984.

برای دانلود رایگان متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

The interaction of cos with Chi is separable from DNA packaging in recA-recBC-mediated recombination of bacteriophage lambda.

Chi (5'-GCTGGTGG) is a recombinator in RecA-RecBC-mediated recombination in Escherichia coli. In bacteriophage lambda vegetative recombination, Chi is fully active only when it is correctly oriented with respect to cos, the site that defines the ends of the packaged chromosome. Here we demonstrate that packaging from cos is not necessary for this cos-Chi interaction. Our evidence suggests that ...

متن کامل

Direction of travel of RecBC recombinase through bacteriophage lambda DNA.

We examined linkage relationships for RecBC-mediated recombination in lytic cycle crosses of lambda phages bearing two cohesive end sites (cos) oriented in the same direction. The relationships obtained imply that a given recombinant tends to be packaged from the cos site that is the nearer one to the right of the exchange. In view of the previously established coupling of entry of a recombinas...

متن کامل

Genetic functions promoting homologous recombination in Escherichia coli: a study of inversions in phage lambda.

We have studied homologous recombination in a derivative of phage lambda containing two 1.4-kb repeats in inverted orientation. Inversion of the intervening 2.5-kb segment occurred efficiently by the Escherichia coli RecBC pathway but markedly less efficiently by the lambda Red pathway or the E. coli RecE or RecF pathways. Inversion by the RecBCD pathway was stimulated by Chi sites located to t...

متن کامل

Homologous recombination in Escherichia coli: dependence on substrate length and homology.

We studied the in vivo recombination between homologous DNA sequences cloned in phage lambda and a pBR322-derived plasmid by assaying for the formation of phage-plasmid cointegrates by a single (or an odd number of) reciprocal exchange. (1) Recombination proceeds by the RecBC pathway in wild-type cells and by low levels of a RecF-dependent pathway in recBC- cells. The RecE pathway appears not t...

متن کامل

RecA433 cells are defective in recF-mediated processing of disrupted replication forks but retain recBCD-mediated functions.

RecA is required for recombinational processes and cell survival following UV-induced DNA damage. recA433 is a historically important mutant allele that contains a single amino acid substitution (R243H). This mutation separates the recombination and survival functions of RecA. recA433 mutants remain proficient in recombination as measured by conjugation or transduction, but are hypersensitive t...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2003