Protein cell distribution question

David N. Levy levy at uab.edu
Sun Dec 20 15:43:11 EST 1998


I have a question about subcellar localization and of proteins. 

I have made a vector that expresses a putative viral protein fused to
GFP and transfected this into HeLa cells.  Unfused WT GFP is
distributed throughout all cells in a diffuse pattern.  My fusion
proteins (I have made both C and N terminal fusions and so far they
have similar phenotypes), on the other hand are mostly distributed in a
distinct punctate pattern.  The interesting thing is that in 90% or so
of the cells the fusion protein is exclusively punctate and nuclear but
in some cells the glowing dots are exclusively cytoplasmic.  In the
rare cell there is apparently a nuclear membrane expression.  The dots
range in size from tiny to huge (know this is a very unscientific
explanation) with the largest being about 1/6 the width of a cell and
the smallest being at the limits of visibility.  Some cells have
hundreds of small dots and some cells have dozens of small dots and ca.
4-8 very large ones.

I know of transcription factors such of NF-Kappa B and gluccocorticoid
receptor molecules which shuttle between the cytoplasm and nucleus, but
is this an all-or-none phenomenon?  And does their distribution vary
like this depending only on cell cycle? (assuming cell cycle is the
factor here).

My putative viral protein is just that: putative, in the sense that
there is an open reading frame in the virus I study, but whether this
orf is translated is not known.  I wonder if this striking pattern is
suggestive of a "real" function, i.e., an indication that this is not
just a random sequence of amino acids.

Thanks.


David N. Levy
University of Alabama at Birmingham
Birmingham, AL 35294-0007

levy at uab.edu


David N. Levy
University of Alabama at Birmingham
Birmingham, AL 35294-0007

levy at uab.edu



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