Molecular and cytogenetic analysis of the heterochromatin-euchromatin junction region of the Drosophila melanogaster X chromosome using cloned DNA sequences.
Molecular and cytogenetic analysis of the heterochromatin-euchromatin junction region of the Drosophila melanogaster X chromosome using cloned DNA sequences.
复制标题
使用克隆的 DNA 序列对果蝇 X 染色体的异染色质-常染色质连接区域进行分子和细胞遗传学分析。
作者：
M. Yamamoto;A. Mitchelson;M. Tudor;K. O'hare;J. Davies;G. Miklos
我们使用三个克隆的DNA序列，包括：(1)分叉转录单元抑制子的一部分，(2)克隆的359-bp卫星，(3)I型核糖体插入，来检查不同染色质类型并放在一起的果蝇X染色体基部的结构。叉形位点抑制子的DNA探针只杂交到20号分裂最近端的多聚部分，形成染色质中心β -异染色质的一部分。克隆的359 bp卫星序列来源于着丝粒和核糖体基因之间的近端有丝分裂异染色质，与染色质中心复制的α -异染色质杂交。I型插入序列主要位于核糖体基因和X染色体的远端有丝分裂异染色质中，如预期的那样与核仁杂交，但不与多粒X染色体的β -异染色质分裂20杂交。我们的分子数据显示，叉状位点的抑制基因非常靠近X染色体的多聚区和非多聚区交界处，从细胞遗传学角度来看，叉状位点是X染色体上最近的普通基因。这些数据对有丝分裂和多丝染色体中β -异染色质- α -异染色质连接区的结构具有启示意义，并参考染色体结构模型进行了讨论。
We have used three cloned DNA sequences consisting of (1) part of the suppressor of forked transcription unit, (2) a cloned 359-bp satellite, and (3), a type I ribosomal insertion, to examine the structure of the base of the X chromosome of Drosophila melanogaster where different chromatin types are found in juxtaposition. A DNA probe from the suppressor of forked locus hybridizes exclusively to the very proximal polytenized part of division 20, which forms part of the beta-heterochromatin of the chromocenter. The cloned 359-bp satellite sequence, which derives from the proximal mitotic heterochromatin between the centromere and the ribosomal genes, hybridizes to the under replicated alpha-heterochromatin of the chromocenter. The type I insertion sequence, which has major locations in the ribosomal genes and in the distal mitotic heterochromatin of the X chromosome, hybridizes as expected to the nucleolus but does not hybridize to the beta-heterochromatic division 20 of the polytene X chromosome. Our molecular data reveal that the suppressor of forked locus, which on cytogenetic grounds is the most proximal ordinary gene on the X chromosome, is very close to the junction of the polytenized and non-polytenized region of the X chromosome. The data have implications for the structure of beta-heterochromatin-alpha-heterochromatin junction zones in both mitotic and polytene chromosomes, and are discussed with reference to models of chromosome structure.