The inhibitor of DNA replication encoded by the Drosophila gene plutonium is a small, ankyrin repeat protein.

Abstract

The plutonium (plu) gene product controls DNA replication early in Drosophila development. plu mutant females lay unfertilized eggs that have undergone extensive DNA synthesis. In fertilized embryos from plu mutant mothers, S‐phase is uncoupled from mitosis. The gene is expressed only in ovaries and embryos, null alleles are strict maternal effect mutations, and the phenotype of inappropriate DNA replication is the consequence of loss‐of‐gene function. plu therefore negatively regulates S‐phase at a time in early development when commitment to S‐phase does not depend on cyclic transcription. plu encodes a protein with two ankyrin‐like repeats, a domain for protein‐protein interaction. plu is immediately adjacent to, but distinct from, the PCNA gene.

giant nucleiis essential in the cell cycle transition from meiosis to mitosis

“…plu, png and gnu are three genes required maternally to inhibit DNA replication in the unfertilised egg and to couple S phase and mitosis in the subsequent embryonic cleavage cycles (Freeman et al, 1986;Freeman and Glover, 1987;Shamanski and Orr-Weaver, 1991;Axton et al, 1994;Elfring et al, 1997;Fenger et al, 2000). Regardless of embryonic genotype, oocytes, eggs and embryos derived from plu, png or gnu homozygous females will be referred to here as plu, png or gnu oocytes, eggs or embryos.…”

Analysis of Ankyrin Repeats Reveals How a Single Point Mutation in RFXANK Results in Bare Lymphocyte Syndrome

“…Indeed, these protein scaffolding modules mediate protein-protein interactions in a number of different biological systems, from microbes to humans (30). The number of ankyrin repeats varies from only 2 in plutonium, a small protein from Drosophila (2), to more than 20 in ankyrin, a well-studied ubiquitous adapter protein that links membrane proteins with the spectrin-based cytoskeleton (23). Elucidation of the three-dimensional structure of the ankyrin repeats by X-ray crystallography and nuclear magnetic resonance techniques offered an insight into their conserved, stable backbone.…”

Drosophila PLUTONIUM protein is a specialized cell cycle regulator required at the onset of embryogenesis.

“…PLU protein levels were maximal in 0-2-h embryos, detectable at low levels in 2-4-h embryos, and undetectable in later embryos. Previous experiments showed that the Plu transcript is undetectable in the larval or pupal stages or in adult males (Axton et al, 1994). The presence of PLU protein during the stages when rapid S-M cycles are occurring, and its absence in later stages, suggests that PLU protein specifically regulates the early division cycles.…”

“…For ectopic expression of PLU in the eye disc, two strategies were used: the pG3.8 plu transgene, which contains all of the sequences necessary for plu function (Axton et al, 1994), was digested with HindIII and SacII to generate a 0.7-kb fragment which contains only six nucleotides 5' to the plu coding region. The ends of this fragment were end-filled using T4 DNA polymerase, and the fragment was cloned into the HpaI site of the pGMR1 vector (Hay et al, 1994).…”

“…We previously cloned the plu gene and demonstrated that it encodes a 19-kDa protein with ankyrinlike repeats (Axton et al, 1994). Here, we analyze the developmental regulation of PLU protein.…”