Position-effect variegation in Drosophila: the modifier Su(var)3-7 is a modular DNA-binding protein

An increase in the dose of the Su(var)3-7 focus of Drosophila augments heterochromatin-promoted variegated silencing. The deduced protein sequence of Su(var)3-7 reveals seven widely spaced zinc fingers. We found that Su(var)3-7 has affinity for DNA in vitro and that the minimal protein sequence requirement for DNA binding is any module containing two zinc fingers and the interval between them. As Su(var)3-7 is a heterochromatin-associated protein, we tested its affinity,for various satellite DNA sequences in vitro. The AATAT and 353-bp elements have the highest affinity. If affinity for satellite DNAs, contributes to the presence of Su(var)3-7 in heterochromatin, a general affinity for DNA, or sequences yet to be determined, suggests a function in the genomic silencing of position-effect variegation: expansion of heterochromatin, whether continuous by spreading or discontinuous by pairing with sequence elements scattered through euchromatin, could use the affinity of Su(var)3-7 for DNA

Premature ovarian failure: morphological and ultrastructural aspects

The authors documented by means of light and transmission electron microscopy that the ovaries of women with premature ovarian failure (POF) displayed dense connective tissue and rare corpora albicantia. Eight of the ten studied cases did not present ovarian follicles; in two cases, it was verified the presence of ovarian follicles, atypical primordial follicles and in one case, a corpus luteum was identified (after stimulation with exogenous gonadotrophin). Regarding the ultrastructural analysis, it was noted that the fibroblasts were united one to each other by cellular prolongations that formed a woof, constituting a cellular syncicius.Os autores analisaram, através de microscopia de luz e de microscopia eletrônica de transmissão, os ovários de mulheres com insuficiência ovariana prematura. Observaram que são constituídos por tecido conjuntivo denso e raros corpos albicantes. Oito dos 10 casos não apresentavam folículos primordiais; em um caso verificou-se a presença de folículos ovarianos atípicos e, em outro, identificou-se corpo lúteo (após estimulação com gonadotrofina exógena). A ultra-estrutura, verificou-se que os fibroblastos achavam-se unidos uns aos outros através de prolongamentos celulares, formando um sincício celular.Escola Paulista de Medicina Department of Obstetrics and GynecologyEscola Paulista de Medicina Department of MorphologyUNIFESP, EPM, Department of Obstetrics and GynecologyEscola Paulista de Medicina Department of MorphologySciEL