Characterization of a Purified Chromatin Acceptor Protein (Receptor Binding Factor 1) for the Avian Oviduct Progesterone Receptor

M. Schuchard, J. J. Rejman, D. J. McCormick, B. Gosse, T. Ruesink, T. C. Spelsberg

Research output: Contribution to journalArticle

19 Scopus citations

Abstract

The specific, high-affinity binding of the avian oviduct progesterone receptor (PR) with target-cell nuclei and chromatin has been shown to involve DNA complexed with specific chromatin acceptor proteins. One of these chromatin acceptor proteins has been partially purified and found to be a small hydrophobic protein with a broad pI of 5.0-6.0 [Goldberger, A., & Speisberg, T. C., (1988) Biochemistry 27, 2103–2109]. This paper describes the final purification over 100 000-fold to apparent homogeneity of this candidate PR acceptor protein, termed the receptor binding factor 1 (RBF-1). When the avian genomic DNA is bound by RBF-1, saturable, high-affinity (KD ~ 2 × 10−9 M) binding sites for PR are generated. RBF-1 has a unique, hydrophobic N-terminal sequence. The PR binding to the RBF-1-DNA complexes is shown to be dependent on an intact activated PR with which excess nonradiolabeled PR can compete. By use of a new, highly specific monoclonal antibody (mAb) to the RBF-1 with Western immunoblotting, RBF-1 was shown to be localized in the nucleus and to be tissue and species specific. Selective removal of the chromatin proteins containing RBF-1 results in the loss of the highest affinity class of PR binding sites. A second class of residual PR binding sites remains in the nucleoacidic protein (NAP), a complex of proteins more tightly bound to the DNA. This class of PR binding activity has been classified as the RBF-2. The RBF-1 is estimated to be 0.03% of the total chromatin protein with about 1.2 × 105 molecules/diploid cell.

Original languageEnglish (US)
Pages (from-to)4535-4542
Number of pages8
JournalBiochemistry
Volume30
Issue number18
DOIs
StatePublished - May 1 1991

ASJC Scopus subject areas

  • Biochemistry

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