c

teiephone Cambridge ( 0223 48011

telex - 81532

27 January 1977

Dr. F. If. C. Crick, FRS,
Tho Sal!; fnstitutc,
Posl Oil'lCt! sax ld09,
Sari Dicgo,
Cali EoL-riia 92112, U.S.A.

Dear Francis,

Tliank you for your letter enclosing the preprint of the paper

with Bak and Zeuthen. It reads very well and I think thc way you
have dealt with the final level of folding can't lead to any
objections. Bak and Zeu-then are both corning to the EM130 Workshop
and one of them will also speak as a discussant in the Royal Society
meeting, It certainly makes a nice story but I still have my doubts
as to whether the original orgaisation of the metaphase chromosome
hasn't been drastically changed by the extraction procedure. 1M hcxy-
leneglycol is rather severel
centration high. I think the paper should have included a short
discussion of this possibility and referred to work on e.m. sections
which don't show a funen.

the times are long and the calcium con-

   Tfimks also for the news about Worcel. Since you left, one
doesn't have the fresh flow of news which may stop one iron getting
into a rut in one's thinking. 1 think I understand the general idea,
but I can't see where the original postu3ate comes from that the
190 base pair repeat, leads to a straight filament.

& -.

I am going to the USA next Monday, 31 Jhhdary, and will be

visiting Rochester all that week.
lectures but I also hope to try to build systematic models of
different types of kink, beginning by seeing what the combination of
our kink and the Sobell kink lead to. In the following week I shall
be at Havcrford College for a fcw days visiting Chris Goff, two days
in i3oston and return to England on the evening of Friday 11 February,
just in time'to get ready for the Royal Society meeting.

Henry Sbbell' aslied me to give some

I should say that my confidence in kinks h2s been diminished

since Len Lutter showed me some patterns of DHAase X digests run on
extendcd gcls where the bands in the 10, 20, 30 rcgion were so
expanded that one could see clear sub-bands corresponding to changes
of oilc base pair. The point is that the bands 1ON k 1, 10N 5 2
aren't 313. that much weaker than the 10N band, suggesting that the cuts
can be made fai.rly easily on either side of the TON bases, albeit
with reduced efficiency. This would be explained naturally by con-
tinuously bent DNA and an enzyme which acts most efficiently at tkie
tno-fold position,but,",as a gradient of activity as thc distortions
from the dvad increase. Len will no doubt tell you about this next

i

r:r. F. H. C. Crick

-2-

27 January 1977

sprc;id might reflect "fraying" at the ends of the CNA during the
oi-j c;inal micrococcal digestion. In answer to this, Len showed me
gels where long chromatin had been digested and which showed the same
ef.Ccct. On close examination, one of the patterns showed the 10N
band less intense than the 1ON Y I bands. So what night be happening
is that these latter bands are produced by subsequent; act.ion of the
l),;,l<isc zr ~CP' one ti the 10, 20 or 30 iong pieces ha; falicii ol€.

---

   We still haven't solved the packing of the crystals and we hzve
bcen much limited by supplies. We are still trying to find
conditions €or reproducible production of the crystals. We had some
excitement when an apparently new form was produced, but it tui-ned
out to be the same crystal structure, but with a quite differelit
habjt. I was, however, encouraged to see that, although the crystals
were even smaller than before, the pattern went out somewhat further
so that the disorder beyond 20 8 may only be dce to the small size
of the crystals. What is new is that we have calculated the 3D
Patterson to a resolution of 25 2 and the section at Z = $, i.e. along
the 340 axis, doesn't show many peaks compared with other sections.
It thus seems, as I have suspected for some time, that there isn't a
trire screw axis parallel to Z and that tne halvings in that direction 5
are low order packing effects.

   John Finch hzs been taking electron micrographs of crystals,
crystal fragments, etc. to try to see if we can correlate them with
the X-ray patterns. Although he has some very nice pictures, the
end effect is to leave one more bewildered than ever. The only thing
one can be reasollably sure of is that the nucleosoriie has a strong
division into t~o pa ts IIcwever it is certainly not'kcmi-somes"
that we have crysta uecause the DNAase I digestion gives a standard
pattern.

$i,skd

We have tried to measure the density seSera1 times and the best

answer we get is somewhere between 8 and 14J I..srn aware of the point
you passed on from Lubert Stryer that, one s'houild lbok not for equil-i-
brium in a flotation method but for a pause in the sinking curve
(indeed we have done this before).

,ciz-s: ;:u t r H&J ,.

/'\

Other news. Vaughn Jackson continues what he began. He gave a

talk the other day at one of our chromatin meetings (which are much
rarer nowadays - I am so busy that I don't always call them) and he
won't move off formaldehyde cross-linking. Ron Lsskey has been
continuicg the search for the assembly intermediate (Barry Honda is now
helping h.im) but recently seems to have come across i? different.
phenomenon. He tried to isolate the relaxing activity on sucrose
gradients and found a beautiful sharp 11s peak. This turns out not to
require histones at all and he believes it may have something to do
with unwinding plus nicking and cutting activi. ty . He theref ore may
$lave stumbled on something to do with replication. However there is a
%wader peak which may contain a partially asseicbled histone inter-
mcd.iate and he is now following that up.

-3-

27 January 1917

Jean Thomas has at last got some reconstitution experiments to

work and certainly the filaments made without WP have a roughly
140 base pair repeat, thus confirming Zachau, but they don't look
any straighter than natural nucleofilanents . The experiments with
reconstitution including €11 arc being done now.

Xhats all for now. Perhaps we can speak on the phone when I

am Xtli ihchester.

Yours ever,

A. Klug

..

8,