The identification of nuclear proteins that bind the homopyrimidine strand of d(GA.TC)n DNA sequences, but not the homopurine strand.

AUTOR(ES)

García-Bassets, I

RESUMO

Alternating d(GA.TC)(n)DNA sequences, which are abundant in eukaryotic genomes, can form altered DNA structures. Depending on the environmental conditions, the formation of (GA.GA) hairpins or [C+T(GA.TC)] and [GA(GA.TC)] intramolecular triplexes was observed in vitro. In vivo, the formation of these non-B-DNA structures would likely require the contribution of specific stabilizing factors. Here, we show that Friend's nuclear extracts are rich in proteins which bind the pyrimidine d(TC)(n)strand but not the purine d(GA)n strand (NOGA proteins). Upon chromatographic fractionation, four major proteins were detected (NOGA1-4) that have been purified and characterized. Purified NOGAs bind single-stranded d(TC)n with high affinity and specificity, showing no significant affinity for either d(GA)n or d(GA.TC)nDNA sequences. We also show that NOGA1, -2 and -3, which constitute the three most abundant and specific NOGA proteins, correspond to the single-stranded nucleic acid binding proteins hnRNP-L, -K and -I, respectively. These results are discussed in the context of the possible contribution of the NOGA proteins to the stabilization of the (GA.GA) and [GA(GA.TC)] conformers of the d(GA.TC)n DNA sequences.

Documentos Relacionados

• The effect of zinc on the secondary structure of d(GA.TC)n DNA sequences of different length: a model for the formation *H-DNA.
• d(GA·TC)n microsatellite DNA sequences enhance homologous DNA recombination in SV40 minichromosomes
• Structural polymorphism of homopurine--homopyrimidine sequences: the secondary DNA structure adopted by a d(GA.CT)22 sequence in the presence of zinc ions.
• Human proto-oncogene N-myc encodes nuclear proteins that bind DNA.
• Formation of DNA triplexes accounts for arrests of DNA synthesis at d(TC)n and d(GA)n tracts.