THE GEORGE WASHINGTON UNIVERSITY

     SCHOOL OF MEDICINE

  133s n STREET, WASHINGTON 5. D. c.

DEPARTMENT OF PHARMACOLOGY

January 7, 1960

Dr. Arthur H. Kornberg
Department of Biochemistq
Stanford University
Palo Alto
California

Dear Arthur:

Thank you very much for your very kind note regarding your recent
I hope you enjoy the trip to Sweden, and that you are able to take
                          I understand this is one of

honors.
advantage of Swedish hospitaliw from now on.
the additional rewards.

Quite recently, while examining some effects of several drugs on

nucleic acid synthesis, I made an observation which surprised me, but which
I have been able to reproduce several times since then.  Labeling Bacillus
cereus with uracil leads to the formation of radioactive pyrimidinr
-and DNA.  We have recently worked out a procedure involving membrane
filters and KOH hydrolysis where we may separate RNA from DNA quantitatively
and most reproducibly.  As a result we have a sensitive way for assaying
quickly the incorporation from a labeled compound into these macromolecul 5.

uracilwbm centrifuged and resuspended so as to remove the label and were
then allowed to continue growing.  During this time, measurements were made
on the relative incorporations into RNA and DNA.  Since, after the centri-
fugation no isotope was present in the medium, it was reassuring to observe
that the total radioactivity per ml. of bacterial suspension remained con-
stant.
rise, apparently at the expense of tht in the RNA.  This would mean that
cells normally growing after the resuspension seem to take bases from the
RNA and converting them into the DNA.

The surprising feature came up in an experiment where cells grown with C 1$ -

However, the relative radioactiviw in the DNA fraction continued to

    Similarly,cells, after a period of growth as above, were allowed to
stand at room temperature rather than being centrifuged and resuspended, and
an identical observation was made.
any DNA was being synthesised, but nevertheless, the relative activiw in
the KOH-insoluble residue ( apparently DNA) kept increasing for a time.

During this standing process I doubt if

Dr. Kornberg

-2-

January 7, 1960

This phenomenon was also observed while standing with exoge  us

used as the label.
I am enclosing two graphs of these results,

uridine plus uracil. Similar observations were made when P !B was

Thus degradation to nucleosides would be excluded.

I am writing you to find out if you have made similar observations,

It may be that I am overlooking something very simple, but then again,
it might be a useful tool for analyzing DNA synthesis.
reason wb the technique should not be an adequate measurement of DNA
synthesis, since it has never failed us in the past.
bility might be a breakdown of RNA, perhaps to the pyrophosphates which
are then converted to the corresponding deoq derivatives, phosphorylated,
and incorporated into DNA.  The drugs (azaguanine and chloroqycefiin)
had no influence on this observation, but allowed it to be made more
clearly because growth was inhibited, although nucleic acid synthesis
was not.

I can see no

One other possi-

I would be interested to hear any comments that you might have

in this regard.

With best wishes,

H. George Mandel
Professor of Pharmacology

graphs enclosed