Hi: A tendency for nuclear localization of GFP is quite often observed in the absence of a NLS. I think it is due to two phenomena: (1) GFP mRNA is higher in concentration around the nucleus, since that is where it is made and exported. This suggests the resultant GFP proteins will be higher in concentration around the nucleus, since they may tend to be translated more efficiently closer to the nucleus. There may also be a gradient of ribosomes (high around the nucleus) since ribosomes are also assembled and exported from the nucleus. (2) GFP assembles as a dimer as it matures. The exclusion limit of nuclear pores is around 40kD. The GFP monomer is about 26kD. This means that monomers that passively penetrate into the nucleoplasm through the nuclear pores may be trapped as assembled dimers inside the nucleus. This will give the appearance of nuclear localization. David At 02:21 AM 5/18/2006, Jan M-B wrote: >Dear Flowers, > >not a flow question, but the expertise is most likely >there. > >Previously I have used eGFP as a transfection control >and was happy enough if the cells were green. > >Now I use eGFP for tagging of proteins and have been >looking at intracellular distribution. My impression >is that the eGFP control (vector pEGFP-n1 from >Clontech, no fusion, COS-7) is everywhere in the cell, >but it is clearly strongest in the nucleus. > >Is this what other people see as well? Is there a >time-course known? > >Regards > >Jan > > > >Jan Mueller-Berghaus, MD >Skin Cancer Unit of the German Cancer Research Center >http://www.dkfz.de/melanom >http://www.aargh.onlinehome.de/burgh/burgh00.htm > >__________________________________________________ >Do You Yahoo!? >Tired of spam? Yahoo! Mail has the best spam protection around >http://mail.yahoo.com David W. Galbraith Professor of Plant Sciences & Professor, Bio5 Institute University of Arizona Office: 822D Marley Building Mailing address: Department of Plant Sciences University of Arizona 303 Forbes Building P.O. Box 210036 Tucson Arizona 85721-0036 USA. Tel: (520) 621-9153 Fax: (520) 621-7186 Email: galbraith@arizona.edu http://latin.arizona.edu/galbraithReceived on Fri May 19 17:38:00 2006
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