The λ and 434 Phage Repressors (original) (raw)

1. Paul Chadwick,
2. Vincenzo Pirrotta,
3. Robert Steinberg,
4. Nancy Hopkins, and
5. Mark Ptashne
6. The Biological Laboratories, Harvard University, Cambridge, Massachusetts

Excerpt

The phenomenon of lysogeny was cited by Jacob and Monod in 1961 as an example of gene control by repressors. It was hypothesized that each temperate phage produces a repressor which specifically blocks the functioning of early genes of that phage. Since the late genes function only if provided with certain early gene products, the proposed repressor action would suffice to turn off all the lytic phage genes, thereby permitting lysogenization. According to these ideas, the dormant phage genes would resume functioning upon removal of the repressor, and it was proposed that inducing agents, such as UV light, function by inactivating the repressor.

Several of the basic aspects of this picture may now be formulated in biochemical terms. The λ and 434 phage repressors, the products of their respective CI genes, have been isolated and their activities explored in vitro (Ptashne, 1967a and 1967b; Pirrotta and Ptashne, 1969). Both repressors