MASSACHUSETTS INSTITUTE 0 F TECHNOLOGY

         CENTER FOR CANCER RESEARCH

  77 MASSACHUSETTS AVENUE, CAMBRl DG E, MASSACHUSETTS 021 39

November 8, 1974

Harold E. Varmus, M.D.
Department of Microbiology
University of California
School of Medicine
San Francisco, California 94122

Dear Harold,

I received your recent letter and I report on our progress,

or more realistically, the lack thereof. We have found the re-
striction enzyme business to be a bloody mess.
from all of our gel work that the proviral form I DNA is hetero-
geneous.
I is RI resistant!  We have heard from Duesberg's lab  that the
fingerprint of our virus has a complexity of 9 x lo6!
things do not appear  to be as simple as we would have liked.
are presently recloning our stock with the hope of simplifying
matters but I fear that Moloney leukemia may be an obligate hetero-
zygote because of different defects in its different virion RNA
subunits.

It is apparent

With RI we get some fragments but a fraction of the form

As such,

We

Although we didn't know the relative contributions of Guntaka

etc. I feel badly about underplaying his role. We sent the paper
off this week and I will attempt to change things at the proof
stage if possible.

With regards to the non-circular forms, we realized that only

a small portion of the material in the top band of EtBr gradient
is really complete form I1 or 111. We have an alkali gradient on
which we will test both our 1251 and 3H-cDNA probes.
there must be quite a bit of single-stranded material there since
we have found that a lot of the proviral DNA is hybridizable to
1251 in the absence of denaturation prior to the hybridization.

I think

Concerning the genea logy of ideas, you might know that I

worked for about 3 years on SV40gand still have a couple things
going.
transcription-translation project which we have here, and I have

We had and have been making SV40 DNA for a coupled

Harold E. Vamrus, M.D.

-2-

November 8, 1974

been making 1.5 mg of SV40 form I at a time (compared with 0.01
pg of Moloney DNA)!!
blue in the face. I had thus scheduled a series of characteriza-
tions of Moloney DNA, this being one of them. But in the end,
talk is cheap,and what I had scheduled to do is  irrelevant.  What
I;i relevant is the fact that you went ahead and did the experiment.
There are always some people hanging around saying that they had
thought of some experiments years before so-and-so went ahead and

So I was running EtBr gradients until I was

did it.
if we appear as such in this manuscript, I will try to correct

I hope that I am not one of these a posteriori seers and

this in future work!

Best wishes,

RAW/mts

Robert A. Weinberg