Berenil-induced undercondensation in human heterochromatin.
The aromatic diamidine berenil specifically inhibits the condensation of a subset of constitutive heterochromatin in human lymphocyte cultures. In the normal male chromosome complement, only the quinacrine-brilliant Y heterochromatin exhibits distinct undercondensation. The optimal culture conditions for inhibiting heterochromatin condensation are achieved when berenil is added at a final concentration of 150 micrograms/ml 24 h before cell harvest. Various examples of the use of berenil in the analysis of chromosome rearrangements involving quinacrine-brilliant heterochromatin are presented. A variant, giant-satellited chromosome 22 was found to respond to berenil treatment, although its enlarged and quinacrine-bright short-arm region did not contain Y heterochromatin. Southern blot analysis and chromosome in situ hybridization suggested that most chromosome 22 variants do not stem from Y; acrocentric translocations. The experimentally undercondensed Y heterochromatin is characterized by moderate C-band labeling, bright quinacrine fluorescence, and specific silver staining. At the ultrastructural level, undercondensation is associated with loosely packed, mutliply folded chromatin fibers with a diameter of approximately 250 A and organized probably as loops.[1]References
- Berenil-induced undercondensation in human heterochromatin. Haaf, T., Feichtinger, W., Guttenbach, M., Sanchez, L., Müller, C.R., Schmid, M. Cytogenet. Cell Genet. (1989) [Pubmed]
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