Nuclear proteins that bind the pre-mRNA 3' splice site sequence r(UUAG/G) and the human telomeric DNA sequence d(TTAGGG)n.
HeLa cell nuclear proteins that bind to single-stranded d(TTAGGG)n, the human telomeric DNA repeat, were identified and purified by a gel retardation assay. Immunological data and peptide sequencing experiments indicated that the purified proteins were identical or closely related to the heterogeneous nuclear ribonucleoproteins (hnRNPs) A1, A2-B1, D, and E and to nucleolin. These proteins bound to RNA oligonucleotides having r(UUAGGG) repeats more tightly than to DNA of the same sequence. The binding was sequence specific, as point mutation of any of the first 4 bases [r(UUAG)] abolished it. The fraction containing D and E hnRNPs was shown to bind specifically to a synthetic oligoribonucleotide having the 3' splice site sequence of the human beta-globin intervening sequence 1, which includes the sequence UUAGG. Proteins in this fraction were further identified by two-dimensional gel electrophoresis as D01, D02, D1*, and E0; intriguingly, these members of the hnRNP D and E groups are nuclear proteins that are not stably associated with hnRNP complexes. These studies establish the binding specificities of these D and E hnRNPs. Furthermore, they suggest the possibility that these hnRNPs could perhaps bind to chromosome telomeres, in addition to having a role in pre-mRNA metabolism.
Ishikawa
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Howard Hughes Medical Institute, Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309-0215.
Matunis
M J
MJ
Dreyfuss
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G
Cech
T R
TR
D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D002467:Cell Nucleus / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D017354:Point Mutation; D012322:RNA Precursors / Q000378:metabolism*; D012326:RNA Splicing; D012091:Repetitive Sequences, Nucleic Acid; D016615:Telomere
D004268:DNA-Binding Proteins; D012322:RNA Precursors