DISTRIBUTION OF THE MAMMALIAN-WIDE INTERSPERSED REPEATS (MIRS) IN THEISOCHORES OF THE HUMAN GENOME

The distribution of MTRs (mammalian-wide interspersed repeats) was inv estigated in 164 human sequences (greater than or equal to 100 kb), wh ich were assigned, according to their GC level, to isochore families L , H1, H2 and H3, MIR elements, whose total number in the genome was es timated to be about 3.3 x 10(5), were found to be unevenly distributed in human isochores. The majority of MIRs (55%) were found in the L is ochore family. Tn contrast, MIR density was highest in H2, closely fol lowed by H1, whereas densities in L and H3 were 2- and 3-fold lower th an in H2, respectively. For this reason, the assessment of MIR distrib ution by inter-repeat PCR led to an overestimation of MIR numbers in H 2 isochore and an underestimation in L isochores, (C) 1998 Federation of European Biochemical Societies.