CTHOMAS@BIONET-20.BIO.NET (Charles Thomas) (01/27/89)
RESEARCH ASSOCIATE POSITION AVAILABLE
HELICON FOUNDATION
SAN DIEGO
January 26, 1989
For the past few years we have been working on the
telomeric DNA sequences of Oxytricha macronuclear DNA. It
is generally agreed that these macronuclear DNA molecules,
which are heterogeneous in length and sequence, can be
represented as:
5' C4A4C4A4C4---2.4 kb---G4T4G4T4G4T4G4T4G4
G4T4G4T4G4T4G4T4G4---average--C4A4C4A4C4
When these telomeres are concentrated to about 0.1
micromolar and incubated in the presence of 0.5 to 1.0 M
NaCl, they stick together to form long concatemeric
structures. Last year we showed that these telomeric
sequences cohere in a specific manner to form a special DNA
structure that has not been described. We call this unusual
DNA structure "COH" for coherence. Sensitive HPLC analysis
indicates that the telomeres are not composed of special or
unusual nucleotides. We know that COH is not a normal DNA
because: 1) it forms 100,000 times more slowly that lambda
sticky ends unite; 2) So far, COH is only formed in the
presence of Na+ - and no other cation tested; 3) once
formed, if placed in K+, the thermal stability of the
concatemers is increased about 25 deg. No other cation that
we tested conferred this increased stability. These
properties were unlike DNA double-helix controls. We
suggest that K+ is chelated or "caged" within the COH, and
in this position it forms additional bonds that stabilize
the structure. Such a cage is likely to be formed by a
multichained molecule (Oka and Thomas, Nucleic Acids Res.
15: 8877-8898 (1987).
We now have synthesized these telomeres and
subjected them to cohering conditions. When examined on
acrylamide gels under stabilizing conditions we find a
variety of more slowly migrating species. These slowly
migrating species have the thermal stability and other
properties that are identical with the native COH. The way
is now open for the production of large amounts of synthetic
COH for NMR and other structural determinations.
HELICON now has a research associate position
available in May to continue this work. The task will be to
determine the structure of COH. This will involve gels and
nucleases, sequencing and footprinting, and finally, with
collaborations, NMR and possibly X-ray diffraction analysis.
If you are interested, please leave me personal
mail on BIONET. I am CTHOMAS. It is also possible to send
me your CV and other materials by this channel; or I may be
reached at the address below. I am very keen to complete
this work.
Yours Sincerely,
Charles A. Thomas,Jr.
HELICON FOUNDATION
4622 Santa Fe Street
San Diego, CA 92109
619 272 3884
-------CTHOMAS@BIONET-20.BIO.NET (Charles Thomas) (02/15/89)
RESEARCH ASSOCIATE POSITION AVAILABLE
HELICON FOUNDATION
SAN DIEGO
January 26, 1989
For the past few years we have been working on the
telomeric DNA sequences of Oxytricha macronuclear DNA. It
is generally agreed that these macronuclear DNA molecules,
which are heterogeneous in length and sequence, can be
represented as:
5' C4A4C4A4C4---2.4 kb---G4T4G4T4G4T4G4T4G4
G4T4G4T4G4T4G4T4G4---average--C4A4C4A4C4
When these telomeres are concentrated to about 0.1
micromolar and incubated in the presence of 0.5 to 1.0 M
NaCl, they stick together to form long concatemeric
structures. Last year we showed that these telomeric
sequences cohere in a specific manner to form a special DNA
structure that has not been described. We call this unusual
DNA structure "COH" for coherence. Sensitive HPLC analysis
indicates that the telomeres are not composed of special or
unusual nucleotides. We know that COH is not a normal DNA
because: 1) it forms 100,000 times more slowly than lambda
sticky ends unite; 2) So far, COH is only formed in the
presence of Na+ - and no other cation tested; 3) once
formed, if placed in K+, the thermal stability of the
concatemers is increased about 25 deg. No other cation that
we tested conferred this increased stability. These
properties were unlike DNA double-helix controls. We
suggest that K+ is chelated or "caged" within the COH, and
in this position it forms additional bonds that stabilize
the structure. Such a cage is likely to be formed by a
multichained molecule (Oka and Thomas, Nucleic Acids Res.
15: 8877-8898 (1987).
We now have synthesized these telomeres and
subjected them to cohering conditions. When examined on
acrylamide gels under stabilizing conditions we find a
variety of more slowly migrating species. These slowly
migrating species have the thermal stability and other
properties that are identical with the native COH. The way
is now open for the production of large amounts of synthetic
COH for NMR and other structural determinations.
HELICON now has a research associate position
available in May to continue this work. The task will be to
determine the structure of COH. This will involve gels and
nucleases, sequencing and footprinting, and finally, with
collaborations, NMR and possibly X-ray diffraction analysis.
If you are interested, please leave me personal
mail on BIONET. I am CTHOMAS. It is also possible to send
me your CV and other materials by this channel; or I may be
reached at the address below. I am very keen to complete
this work.
Yours Sincerely,
Charles A. Thomas,Jr.
HELICON FOUNDATION
4622 Santa Fe Street
San Diego, CA 92109
619 272 3884
-------SELD1020@hasara11.bitnet (grace) (02/17/89)
this is only a try out from moi
hope this will work