Provirus integration into a gene encoding a ubiquitin-conjugating enzyme results in a placental defect and embryonic lethality.

Abstract

(2). Very recent evidence suggests that ubiquitination of membrane-bound receptors might also serve as a signal for degradation via the lysosomal pathway (4). Although ubiquitin conjugation is mainly thought to tag proteins for destruction, several lines of evidence suggest that it might also be involved in other cellular functions. This is indicated, for example, by the presence of stable ubiquitinated proteins, such as histones (5), and by the existence of enzymes that remove ubiquitin from conjugates and therefore make this modification reversible (6). Reversible ubiquitination might have a role in modulating the function of target proteiIns similar to protein phosphorylation. Attachment of ubiquitin to cellular proteins is carried out by the sequential action of three classes of enzymes, ubiquitinactivating enzymes (referred to as El or Uba), ubiquitinconjugating enzymes (E2 or Ubc), and ubiquitin-protein ligases (E3 or Ubr) (7). In an initial activating step the El enzyme forms a thiolester bond with the C terminus of ubiquitin, which is then transferred to a specific cysteine residue of the E2 enzyme. Although E2 enzymes can directly donate ubiquitin to proteins, E3 enzymes are typically required for recognition of specific proteolytic substrates and at least in one case have been shown to be directly involved in the final transfer of ubiquitin to a substrate protein (8). E2 enzymes are encoded by a multigene family and several members of this family have been isolated from various organisms including plants. The function of E2 enzymes has been studied most extensively in yeast by usiing a genetic approach. Mutations in individual genes for dlifferent yeast E2 enzymes revealed that these proteins participate in a wide variety of essential cellular functions (1). In Drosophila an E2 enzyme has been shown to be involved in nervous system development (9, 10). Based on these results it is most likely that in higher organisms, including man, mutations in the genes coding for the different enzymes of the ubiquitin-conljugating system will contribute to abnormal development and disease. Indirect evidence for such a relationship has accumulated over the past years (11).No mouse mutants with spontaneous or experimentally induced alterations have been previously described that help to clarify the role of any of the E2 genes during differentiation and development. In the present report we describe a transgenic mouse mutant where integration of a retrovirus into an E2 gene, designated UbcM4, results in a recessive-lethal phenotype. Homnozygous embryos die in utero most likely as a result of impaired placenta development. MATERIALS AND METHODSDerivation of A6 Mouse Strain. Cells of the embryonal stem (ES) cell line JI (12) were intfected by growing on a monolayer of x-ray irradiated Psi-2 cells producing niplO virus (13) in ES cell culture medium containing 8 ,rg/ml polybrene. After coculture for 48 h, ES cells were trypsinized and selected in medium containing G418 (125 p,g/ml of active component) for 10 days. G418-r...

Differentially expressed genes implicated in embryo abortion of mango identified by suppression subtractive hybridization

“…Functional analyses of potential ubiquitin-conjugating enzymes have been well-documented in mammalian cells. Evidence suggests that ubiquitin-conjugating E2 enzyme is essential for male fertility in mouse (Roest et al, 1996), and provirus integration into a gene encoding a ubiquitin-conjugating enzyme results in a placental defect and embryonic lethality (Harbers et al, 1996). However, its function in parthenogenesis has not been determined.…”

A family of structurally related RING finger proteins interacts specificallywith the ubiquitin‐conjugating enzyme UbcM41

“…Based on our previous observation that inactivation of UbcM4 in mice is most likely responsible for abnormal placenta development [6], we speculate that the UIPs, in analogy to Sina, link the ubiquitin/proteasome system to proteins involved in placenta development. Experiments are under way to confirm our hypothesis by isolating and characterizing other proteins that interact with the UIPs and by eventually identifying in vivo target proteins of UbcM4.…”

“…We recently described a transgenic mouse mutant where partial inactivation of the gene for the ubiquitin-conjugating enzyme UbcM4 resulted in a recessive-lethal phenotype [6]. Homozygous embryos die in utero most likely as a result of placenta impairment.…”

Knock-in of integrin β1D affects primary but not secondary myogenesis in mice

“…We examined the distribution of laminin, a marker for foetal blood vessels (Harbers et al, 1996), in placentae of E14.5 embryos. The results showed that embryonic blood vessels present in the labyrinth of both heterozygous and morphologically normal, living β1D ki/ki embryos were uniform in diameter and regularly spaced ( Fig.…”