Hoover K K, Chien A J, Corces V G
Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218.
Genetics. 1993 Oct;135(2):507-26. doi: 10.1093/genetics/135.2.507.
The products of the forked gene are involved in the formation and/or maintenance of a temporary fibrillar structure within the developing bristle rudiment of Drosophila melanogaster. Mutations in the forked locus alter this structure and result in aberrant development of macrochaetae, microchaetae and trichomes. The locus has been characterized at the molecular level by walking, mutant characterization and transcript analysis. Expression of the six forked transcripts is temporally restricted to mid-late pupal development. At this time, RNAs of 6.4, 5.6, 5.4, 2.5, 1.9 and 1.1 kilobases (kb) are detected by Northern analysis. The coding region of these RNAs has been found to be within a 21-kb stretch of genomic DNA. The amino terminus of the proteins encoded by the 5.4- and 5.6-kb forked transcripts contain tandem copies of ankyrin-like repeats that may play an important role in the function of forked-encoded products. The profile of forked RNA expression is altered in seven spontaneous mutations characterized during this study. Three forked mutations induced by the insertion of the gypsy retrotransposon contain a copy of this element inserted into an intron of the gene. In these mutants, the 5.6-, 5.4- and 2.5-kb forked mRNAs are truncated via recognition of the polyadenylation site in the 5' long terminal repeat of the gypsy retrotransposon. These results help explain the role of the forked gene in fly development and further our understanding of the role of transposable elements in mutagenesis.
叉状基因的产物参与了黑腹果蝇发育中的刚毛原基内临时纤维状结构的形成和/或维持。叉状基因座的突变会改变这种结构，并导致大刚毛、小刚毛和毛状体的异常发育。该基因座已通过染色体步移、突变体鉴定和转录本分析在分子水平上得到了表征。六种叉状转录本的表达在时间上局限于蛹发育的中后期。此时，通过Northern分析可检测到6.4、5.6、5.4、2.5、1.9和1.1千碱基（kb）的RNA。已发现这些RNA的编码区位于一段21 kb的基因组DNA内。由5.4 kb和5.6 kb叉状转录本编码的蛋白质的氨基末端包含锚蛋白样重复序列的串联拷贝，这可能在叉状编码产物的功能中起重要作用。在本研究中表征的七个自发突变中，叉状RNA的表达谱发生了改变。由吉普赛逆转录转座子插入诱导的三个叉状突变包含该元件的一个拷贝插入到基因的一个内含子中。在这些突变体中，5.6 kb、5.4 kb和2.5 kb的叉状mRNA通过识别吉普赛逆转录转座子5'长末端重复序列中的聚腺苷酸化位点而被截断。这些结果有助于解释叉状基因在果蝇发育中的作用，并进一步加深我们对转座元件在诱变中的作用的理解。
