Integration of two sets of T7 mutants

VIROLOGY

39,587-588

(1969)

Short Integration

of Two

Communications

Sets of T7 Mutants

A number of amber complementation groups of T7 have been isolated and described independently by Hausmann and Gomez (1) and by Studier (2). The purpose of this communication is to report the integration of these two sets of mutants and to summarize and compare the physiological data presently available about them. The data are given in Table 1. We adopt the numbering used by Studier, where genes are numbered from left to right (l-19) according to their position on the map. Representatives from each set of complementation groups were tested against each other by spot tests, and assignments were confirmed by complementation tests in liquid culture, by mapping, or both. Each of the complementation groups of Hausmann and Gomez falls into one of the 19 genes of Studier; genes 2 and 10 are not represented in the Hausmann and Gomez collection. Incorporation of tritiated thymidine into acid-precipitable material was used in both of the above studies to measure DNA synthesis, Hausmann and Gomez (1) measuring the total uptake in W-irradiated host cells, and Studier (2) measuring the rate of uptake in a series of 30-second pulses in normal host cells. The two sets of data agree that essentially no phage DNA is synthesized after infection of the restrictive host with most mutants in genes 1,4 or 5, which correspond to DO-A and the two DO-B complementation groups of Hausmann and Gomez. Studier found that mutants in genes 2,3, and 6 (and 4, to a small extent) begin to synthesize phage DNA but shut off prematurely; Hausmann and Gomez reported a reduced total synthesis in their mutant from gene 6 but an essentially normal amount of synthesis in the mutant from gene 3. Both sets of experiments found normal DNA synthesis in mutants from genes 7-19.

In a normal infection by wild-type T7, tritiated thymidine is incorporated first into a rapidly sedimenting form of T7 DNA and is then chased into phage-sized pieces; such maturation can be prevented by the addition of chloramphenicol (3, 4). Hausmann and LaRue (3) have examined the sedimentation behavior of newly-synthesized DNA using mutants from many of these T7 genes; their results can be compared with what is known about the ability of mutants from the same genes to synthesize DNA, to form DNAcontaining particles, or to synthesize specific proteins (2, 5). The DNA which is synthesized after infection with mutants in genes 3 and 6 is found primarily in pieces which are smaller than phage size (S), a result which is probably related to the premature cessation of DNA synthesis when phage are defective in these genes (2). DNA made after infection with mutants in genes7, 11, 12, 13, or 17 has a sedimentation pattern very similar to what is found in a wild-type infection (3), and mutants in these genes also make stable, DNA-containing particles (2, 5). Some maturation of the DNA also occurs in mutants of genes 14, 15, and 16 (S), which do not form stable, DNA-containing particles (2, 5), but a smaller fraction of the DNA seemsto be in phage-sized pieces. Essentially no maturation of the DNA is found in mutants of genes 8, 9, 18, or 19 (3). Gene 8 specifies a protein found in purified phage particles, and gene 9 specifies a protein which is found in top component but not in DNA-containing particles (5). It is possible that a structure containing these two proteins might be necessary for maturation to proceed, and that the phage-sized pieces of DNA do not remain stably associated with such a structure in the absenceof the products of genes 14, 15, and 16. In this regard it would be interesting to know if maturation of the DKA occurs in mutants of gene 10, which specifiesthe major protein

587

588

Studier” Gene

1

Hausmann

Mutant

64 29 20 28 147 405 11 17 13 37 88 149 140 31

16

9

17 18

8 182

Mutam

1 11

H28O’i H13 /

19

10

14 17

1171 H108

P2(tail)

15 13

H80 H51

Sedimentation pattern of newly synthesized DNAd

*

Small

pieces

Small

pieces

Partially degraded Normal No maturation No maturation

+ P4b TC P6 (head)

H20 All A21 Gomez

DNA c synthesis”

0

HI0 H131 H30 H5 N72 H127 H6

a Studier (2). b Hausmann and

ljarticles”

ES ES 0 (ES?) 0 ES

9 3 2 7 20 19 8

12 4 5

DNA-containing

Phage proteins”

Group

23

2 3 4 5 G 7 8 9 10 11 12 13 14 15

*

+ + +

Normal Normal Normal Partial

maturation

P3

Partial

maturation

Pl

Normal

or partial

+

P4a(final)

maturation

Normal No maturation No maturation

(1).

c Studier and Maize1 (5). d Hausmann

and

Abbreviations: top component

LaRue

(3).

P stands for a protein but

not

found in phage particles;

in DNA-containing

particles;

subunit of the phage head (5) and might be expected to be included in such a structure. The products of genes 18 and 19 are not known to be associated with any phagerelated structures; they might represent enzymes involved in the maturation process.

ES stands 2. STUDIER, 3. HAUSMANN,

TC stands for a protein

for early

shut-off

F. W., Virology R.,

and LARUE,

REFERENCES 1. HAUSM~NN,

R.,

779-792 (1967).

and

GoM~:z,

B., J. Virology

found in synthesis.

39, 562-574 (1969). K., J. Virology 3,

278-281 (1969).

4. KELLY,

T. J., JR., and THOMAS, Mol. Biol., in press. 5. STUDIER, F. W., and MAIZEL, J. 39, 575-586 (1969).

ACKNOWLEDGMENTS Portions of this research were carried out at Brookhaven National Laboratory under the auspices of the U. S. Atomic Energy Commission, and at the Institut fiir Genetik in Freiburg, West Germany.

of DNA

Biology

C. A., JR.,

V., JR., Virology

F. WILLIAM

Department

Brookhaven National Laboratory Upton, New York ii973 R. HAUSMANN Institut fiir Genetik der Universitiit Freiburg 78 Freiburg i. Br., Sctinzlestr. g-11, West Germany

1, Accepted

July

22, 1969

STUDIER

J.