fc177, a Minor dec-1 Proprotein, Is Necessary to Prevent Ectopic Aggregation of the Endochorion During Eggshell Assembly in Drosophila

The Drosophila eggshell is a highly specialized extracellular matrix that forms between the oocyte and the surrounding epithelial follicle cells during late oogenesis. The dec-1 gene, which is required for proper eggshell assembly, produces three proproteins that are cleaved within the vitelline membrane layer to multiple derivatives. The different spatial distributions of the cleaved derivatives suggest that they play distinct roles in eggshell assembly. Using extant dec-1 mutations in conjunction with genetically engineered dec-1 transgenes, we show that, although all three dec-1 proproteins, fc106, fc125, and fc177, are required for female fertility, gross morphological abnormalities in the eggshell are observed only in the absence of fc177. The coalescence of the roof, pillar, and floor substructures of the tripartite endochorion suggested that quantitatively minor fc177 derivatives are necessary to prevent ectopic aggregation of endochorion proteins during the assembly process. Expression of a fc177 cDNA in dec-1 null mutants was sufficient to restore spaces within the endochorion layer. Fc177 may function as a scaffolding protein akin to those utilized in viral morphogenesis

Immunological analysis of human chromosomal proteins

Summary available: p. xviii

The essential JIL-1 kinase regulates histone H3 phosphorylation and maintains chromatin structure in Drosophila

JIL-1 encodes a chromatin-associated tandem serine/threonine kinase in Drosophila melanogaster. JIL-1 predominantly associates with interbands on polytene chromosomes. It appears at higher levels on the X chromosome than on autosomes in males, and distributes about equally on all chromosomes in females. In addition, in males JIL-1 overlaps with the MSL (for male specific lethal) complex that specifically associates with the male X chromosome on which expression of most genes are upregulated.;We isolated JIL-1 mutants by inducing imprecise excision of an EP element inserted in JIL-1. We found that JIL-1 is required for viability of both females and males, but male viability is more sensitive to reduction of JIL-1 levels. Additionally, JIL-1 is required for embryogenesis, oogenesis and segment identity. Polytene chromosomes from JIL-1 mutant third instar larvae are shortened, coiled and lose their banding patterns, suggesting that JIL-1 plays a role in maintaining higher order chromatin structure. JIL-1 mutants show reduced levels of histone H3 serine10 (ser10) phosphorylation. The higher level of histone H3 ser10 phosphorylation on the male X chromosome is dependent upon JIL-1. However, the level of histone H3 ser10 phosphorylation in mitotic cells is similar between JIL-1 mutants and wild type, suggesting that JIL-1 mainly controls histone H3 ser10 phosphorylation in interphase.;JIL-1 kinase domain I (KDI) interacts with Lola ZF5, a splice isoform of the lola locus. Most Lola isoforms belong to the class of BTB (for b&barbelow;ric-a-brac, t&barbelow;ramtrack, and B&barbelow;road-complex) domain containing zinc finger proteins while two of them contain no zinc finger motif. A lola P-element mutation potentially disrupting all isoforms partially suppresses the reduced hatch rate phenotype in JIL-1EP(3)3657/JIL-1 EP(3)3657 embryos. The mode of interaction between lola and JIL-1 is consistent with the general nature of BTB zinc finger proteins as transcription repressors, and suggests possible mechanisms through which other proteins can modify JIL-1 functions or JIL-1 regulates other proteins involved in chromatin organization