Identification of recombination events resulting in three hybrid genes
encoding human MiV, MiV(J.L.), and Sta glycophorins
CH Huang and OO Blumenfeld
Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY.
MiV, MiV(J.L.), and Sta glycophorins specify the respective variant
phenotypes of the human MNSs blood group system. We report that unequal but
homologous crossing-over between alpha and delta glycophorin genes results
in three hybrid genes encoding MiV, MiV(J.L.), and Sta glycophorins.
Restriction mapping and allele-specific oligonucleotide hybridization
grossly defined the third intron as the probable crossing- over site and
showed that MiV and MiV(J.L.) genes are arranged in the same 5' alpha-delta
3' frame whereas Sta gene is in a reciprocal 5'delta-alpha 3'
configuration. Genomic sequences spanning the extracellular domain exons 2
to 4 were amplified from each variant gene by polymerase chain reaction and
determined by direct DNA sequencing. Comparison of nucleotide sequences
encompassing the third intron showed that the three hybrid genes differed
in location of crossing-over sites. The alpha-delta breakpoints in MiV and
MiV(J.L.) genes were localized to the 3' end of the HindIII site downstream
from exon 3 and to the 5' end immediately upstream from exon 4,
respectively, whereas the delta-alpha breakpoint in Sta gene resided in
between. An AAAGT sequence oriented in either forward or reverse direction
was identified within the crossing-over region of each hybrid gene whose
surrounding sequences bear a strong local strand asymmetry. The single
nucleotide substitution in exon 4 of MiV and MiV(J.L.) genes (ACG [Thr] to
ATG [Met]) demonstrated that the two genes differed in the delta
glycophorin alleles that must have participated in the recombination.
Volume 77,
Issue 8,
pp. 1813-1820,
04/15/1991
Copyright © 1991 by The American Society of Hematology
