A Xenopus egg factor with DNA-binding properties characteristic of terminus-specific telomeric proteins.
We have identified a Xenopus laevis protein factor that specifically recognizes vertebrate telomeric repeats at DNA ends. This factor, called Xenopus telomere end factor (XTEF), is detected predominantly in extracts of Xenopus eggs and ovaries, which are estimated to contain sufficient XTEF to bind approximately 3 x 10(7) DNA ends. In contrast, XTEF is much less abundant (approximately 90 per cell) in extracts of somatic cell nuclei. Mobility retardation analysis of the XTEF activity in egg extracts indicates that this factor binds the vertebrate telomeric repeat sequence (TTAGGG)2 when present in a single-stranded 3' overhang. Single-stranded 3' extensions of (TTTGGG)2, (AAAGGG)2, (TTACCC)2, or a nonrepetitive sequence fail to bind XTEF efficiently, whereas changes in the double-stranded sequence 5' to the TTAGGG repeat tail are tolerated. TTAGGG repeats are not recognized at internal position, at a 5' protruding end, or in double-stranded DNA. In addition, the factor does not bind RNA with single-stranded UUAGGG repeats at a 3' end. XTEF-DNA complexes form and are stable in high salt. The DNA-binding properties of XTEF resemble the characteristics of a class of terminus-specific telomere proteins identified previously in hypotrichous ciliates.
Cardenas
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ME
Rockefeller University, New York, New York 10021-6399.
Bianchi
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A
de Lange
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D000085:Acetates / Q000494:pharmacology; D019342:Acetic Acid; D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D005786:Gene Expression Regulation; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism*; D012313:RNA / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D016615:Telomere / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology; D014982:Xenopus laevis
D000085:Acetates; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D012313:RNA; D004247:DNA; D019342:Acetic Acid