Fanconi anaemia cells are not uniformly deficient in unhooking of DNA interstrand crosslinks, induced by mitomycin C or 8-methoxypsoralen plus UVA.

Fanconi anaemia (FA) cells are extremely sensitive to crosslinking agents, e.g. mitomycin C, but only moderately sensitive to trimethylpsoralen plus UVA. Evidence has been reported suggesting that there is a deficient DNA crosslink repair mechanism in FA cells, but others failed to confirm this conclusion using other methods and other crosslinking agents. We reinvestigated the mitomycin C and 8-methoxypsoralen crosslink repair in FA cells with a high sensitivity to mitomycin C. Although an essentially similar methodology was used to that previously described, no difference between the control and FA cell strains was observed, neither for mitomycin C- nor for 8-methoxypsoralen-induced crosslinks.

Assignment of human transcobalamin II (TC2) to chromosome 22 using somatic cell hybrids and monosomic meningioma cells.

Human transcobalamin II (TC2), a vitamin B12 binding serum protein, is synthesized and secreted into the medium by cells growing in vitro. Mouse-man somatic cell hybrids were analyzed in order to map the locus of TC2. The presence of human TC2 in the culture media was correlated with the results of genetic marker and chromosome analysis of the hybrid cells. Chromosome 22 showed 100% concordancy. However, chromosome 6 (90% concordancy) and chromosome 7 (96% concordancy) were not completely excluded. Meningioma cells obtained from patients heterozygous for TC2 showed a concomitant loss of one chromosome 22 and one of the TC2 alleles, strongly supporting the assignment to chromosome 22.