Characterization of Hmbp-2, a Dna-Binding Protein That Binds to Hiv-1 Ltr When Only One of the Three Sp1 Sites Is Methylated

HIV-1 methylation binding protein-1 (HMBP-1) (formerly called HMBP) is a protein found in human cell nuclei that binds with enhanced affinity to a fragment of the HIV-1 long terminal repeat sequence (LTR) containing three Sp1 sites when all three sites are methylated. HMBP-2 is another protein present in the nuclei of human T helper lymphocytes and HeLa cells that binds to the HIV-1 LTR. HMBP-2 binds preferentially to the same region of the HIV-1 LTR as does HMBP-1, but HMBP-2 binds best when only one of the three Sp1 sites is methylated. HMBP-2 can be separated from HMBP-1 chromatographically, and dimethyl sulfate (DMS) methylation interference analysis indicates that their binding sites are not identical. HMBP-2 represents a novel protein factor capable of binding to a partially methylated region of the HIV-1 LTR. [References: 23]

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