The Drosophila homolog of the mammalian imprint regulator, CTCF, maintains the maternal genomic imprint in Drosophila melanogaster.

Background: CTCF is a versatile zinc finger DNA-binding protein that functions as a highly conserved epigenetic transcriptional regulator. CTCF is known to act as a chromosomal insulator, bind promoter regions, and facilitate long-range chromatin interactions. In mammals, CTCF is active in the regulatory regions of some genes that exhibit genomic imprinting, acting as insulator on only one parental allele to facilitate parent-specific expression.

Mosaic genetic screen for suppressors of the de2f1 mutant phenotype in Drosophila.

The growth suppressive function of the retinoblastoma (pRB) tumor suppressor family is largely attributed to its ability to negatively regulate the family of E2F transcriptional factors and, as a result, to repress E2F-dependent transcription. Deregulation of the pRB pathway is thought to be an obligatory event in most types of cancers. The large number of mammalian E2F proteins is one of the major obstacles that complicate their genetic analysis.

Cellular responses to endoplasmic reticulum stress and apoptosis.

The endoplasmic reticulum (ER) is the cell organelle where secretory and membrane proteins are synthesized and folded. Correctly folded proteins exit the ER and are transported to the Golgi and other destinations within the cell, but proteins that fail to fold properly-misfolded proteins-are retained in the ER and their accumulation may constitute a form of stress to the cell-ER stress. Several signaling pathways, collectively known as unfolded protein response (UPR), have evolved to detect the accumulation of misfolded proteins in the ER and activate a cellular response that attempts to maintain homeostasis and a normal flux of proteins in the ER.

dE2F2-independent rescue of proliferation in cells lacking an activator dE2F1.

In Drosophila melanogaster, the loss of activator de2f1 leads to a severe reduction in cell proliferation and repression of E2F targets. To date, the only known way to rescue the proliferation block in de2f1 mutants was through the inactivation of dE2F2. This suggests that dE2F2 provides a major contribution to the de2f1 mutant phenotype.

Specific role of the SR protein splicing factor B52 in cell cycle control in Drosophila.

E2F and retinoblastoma tumor suppressor protein pRB are important regulators of cell proliferation; however, the regulation of these proteins in vivo is not well understood. In Drosophila there are two E2F genes, an activator, de2f1, and a repressor, de2f2. The loss of de2f1 gives rise to the G(1)/S block accompanied by the repression of E2F-dependent transcription.

The eukaryotic DNMT2 genes encode a new class of cytosine-5 DNA methyltransferases.

DNMT2 is a subgroup of the eukaryotic cytosine-5 DNA methyltransferase gene family. Unlike the other family members, proteins encoded by DNMT2 genes were not known before to possess DNA methyltransferase activities. Most recently, we have shown that the genome of Drosophila S2 cells stably expressing an exogenous Drosophila dDNMT2 cDNA became anomalously methylated at the 5'-positions of cytosines (Reddy, M.