Recombinational resolution in primate cells of two homologous human DNA segments with a gradient of sequence divergence.
AUTOR(ES)
Gomez-Pedrozo, M
RESUMO
Human alpha-thalassemia-2 genotype -alpha 4.2 is the result of meiotic recombination between two 1.3 kb long, homologous DNA segments, X(alpha 2) and X(alpha 1), located in the adult alpha globin locus. The two segments can also undergo intramolecular recombination on extrachromosomal vectors transfected into mitotically dividing primate cells (COS 7). The existence of a gradient of sequence divergence between X(alpha 2) and X(alpha 1) makes them an interesting system to study the relationship between efficiencies of homologous DNA recombination and the extent of dispersed and localized base mismatches. By partial restriction mapping and DNA sequencing of plasmids recombined in COS 7 cells and rescued from bacteria HB 101, we have determined the distribution of recombinational resolution sites along the two X blocks. Most, if not all, of the homologous recombination events between the two X blocks appear to be single crossing-over without efficient gene correction or repair of base mismatches. The distribution of the sites of recombinational resolution is inversely correlated with that of the gradient of sequence divergence, with only approximately 7% of the X recombinants resolved within the 3' third of the X blocks where two diverged Alu family repeats reside. The Alu sequence within which one of the X recombinants resolved is homologous to a previously characterized alpha thalassemia deletion point.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=339007Documentos Relacionados
- Interference of DNA sequence divergence with precise recombinational DNA repair in mammalian cells.
- Kinetoplast DNA minicircles: regions of extensive sequence divergence.
- Three human alcohol dehydrogenase subunits: cDNA structure and molecular and evolutionary divergence.
- An rRNA variable region has an evolutionarily conserved essential role despite sequence divergence.
- Rate of divergence of cellular sequences homologous to segments of Moloney sarcoma virus.