Nuclear factors specifically bind to upstream sequences of a Xenopus laevis ribosomal protein gene promoter.

AUTOR(ES)

Carnevali, F

RESUMO

The upstream region of the Xenopus laevis L14 ribosomal protein gene was deleted starting from the 5' extremity in order to define the promoter length necessary to express a linked reporter CAT gene. The functional analysis indicated that a sequence located between -63 and -49 from the capsite is important for an efficient promoter activity. Band shift and ExoIII protection assays evidenced the binding to this region of a factor, called XrpFI, present in the crude nuclear extract from X.laevis oocytes. Methylation interference analysis localized the contacts in the G residues belonging to a short box, 5' CTTCC 3', positioned between -53 and -49 from the capsite. An additional factor, XrpFII, makes contacts with the sequence 5'GCCTGTTCGCC 3' located between -27 and -17 from the capsite. The deletion mutant still containing this sequence is poorly transcribed, but resumes activity when a short fragment containing the binding site for factor XrpFI is cloned in an upstream position.

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