Affinity Purification of Alu-DNA-Repeat-Binding Proteins from Human Somatic Cells

D. V. Luk'yanov^*, G. F. Reshetnikova, and O. I. Podgornaya

Institute of Cytology, Russian Academy of Sciences, Tikhoretskii pr. 4, St. Petersburg, 194064 Russia; fax: (812) 520-9703; E-mail: podg@ivm.stud.pu.ru

^* To whom correspondence should be addressed.

Received June 22, 1998; Revision received August 28, 1998

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A 66-kD Alu-DNA-repeat binding protein was identified in human somatic cell nucleoplasm. Gel shift assay, southwestern blotting, and affinity purification on DNA attached to a carrier were used. A 60-kD protein copurified with the 66-kD protein during affinity purification, probably due to protein--protein interactions. The gel shift assay reveals multiple complexes with exponential dependence of their relative mobility. The short binding site of the 66-kD protein was defined with the help of synthetic oligonucleotides. It is localized between the A and B boxes of RNA polymerase III promotor and is the same as that reported for the Alu-binding protein from human spermatozoids. The same short binding site, the similarity of the isolation procedure from germ and somatic cells, and similar binding properties and molecular masses suggest homology of the two proteins. The relationship of the proteins we studied and the Alu-DNA-binding proteins described in the literature is discussed.

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KEY WORDS: site-specific DNA--protein binding, Alu-repeat, Alu-DNA-binding proteins

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