Disease relevance of UBE1

• The product expressed in Escherichia coli exhibited the ability to form a thiol ester linkage with ubiquitin in a ubiquitin-activating enzyme E1-dependent manner [1].
• The A1S9 gene appeared to be larger than the DNA recovered in individual phage isolates, as was assessed by transfection experiments [2].

High impact information on UBE1

• The human X-linked gene A1S9 complements a temperature-sensitive cell-cycle mutation in mouse L cells, and encodes the ubiquitin-activating enzyme E1 [3].
• A candidate spermatogenesis gene on the mouse Y chromosome is homologous to ubiquitin-activating enzyme E1 [3].
• Cell lines expressing temperature-sensitive mutants of the tumor suppressor protein p53, the viral oncogene protein pp60src, or a ubiquitin activating enzyme E1, were incubated at the nonpermissive temperature (39.5 degrees C) in the presence of glycerol, trimethylamine N-oxide or deuterated water [4].
• Human cell lines harbouring increasing numbers of inactive X chromosomes (47, XXX, 49, XXXXX) were found to express the A1S9 gene at the same level as control cells (45, X), suggesting that the gene does not escape X chromosome inactivation [5].
• The temperature-sensitive ts A1S9 mutation of mouse L cells was previously shown to affect nuclear DNA replication and to be complemented by active and inactive human X chromosomes in human-ts A1S9 somatic cell hybrids [5].

Biological context of UBE1

• And third, sites at the 5' end of UBE1 are unmethylated on both active and inactive X chromosomes, consistent with the gene escaping inactivation [6].
• Here we present three lines of evidence that UBE1 is expressed from the inactive X chromosome and therefore escapes X inactivation [6].
• Second, UBE1 is expressed in a large panel of somatic cell hybrids retaining inactive human X chromosomes, including two independent hybrids that did not require UBE1 expression for survival [6].
• We have uniquely placed UBE1 and the SYN1 gene cluster in a 330-kb YAC within the contig [7].
• By in situ hybridization to metaphase chromosomes from male mice and by Southern blot analysis of male and female mouse DNA, we show that, in the mouse, a human UBE1 cDNA probe identified both X- and Y-linked loci [8].

Anatomical context of UBE1

• First, by RNA in situ hybridization, UBE1 RNA is detected from both the active and inactive X chromosomes in human female fibroblasts [6].
• The nucleotide sequence of the human cDNA encoding ubiquitin-activating enzyme E1 is more than 99% identical with the human A1S9T cDNA, a gene that has been shown to complement the temperature-sensitive mutant mouse cell line, tsA1S9 [8].
• The expression of three mouse X-chromosome genes, Rps4, Zfx, and Ube1 was examined by reverse transcriptase polymerase chain reaction (RT-PCR) in heterozygous cultured cells from a cross of a laboratory mouse by Mus spretus, which were selected to uniformly express the X chromosome from the laboratory mouse parent [9].
• Functional studies of the mutant proteins with the ubiquitin-activating enzyme E1 and in the reticulocyte protein degradation assay were used to identify regions of the molecule important to ubiquitin's activity in intracellular proteolysis [10].
• The concerted expression of these genes together with other genes related to cell protection and cell cycle like DnaJ, p21(cip1) and the ubiquitin activating enzyme E1 demonstrates the identification of new genes in the context of TNF-alpha induced gene expression patterns mediating the prosurvival effect of TNF-alpha in endothelial cells [11].

Associations of UBE1 with chemical compounds

• Conserved structure and amino acid sequence analysis revealed that the protein contained 1 Thif-domain, 2 UBACT-domains, and a functional active site cysteine lay upstream of UBACT domain, all of them also existed in ubiquitin-activating enzyme E1 and E1 like proteins [12].
• The inability of penta-ubiquitin to act as a substrate in the pyrophosphate exchange reaction with the ubiquitin-activating enzyme E1 suggested that it had a carboxyl-terminal Asn, in agreement with the nucleotide sequence [13].
• There is no change in synthesis of the constitutive form of SP 70 or of the ubiquitin activating enzyme E1 during heat shock or glucose starvation [14].
• We have used the ubiquitin-activating enzyme E1 and one of the ubiquitin-conjugating enzymes E2 to attach a fluorescent lysine derivative to the C terminus of ubiquitin [15].

Regulatory relationships of UBE1

• A 420-kb YAC clone positive for PCTK1 also contains the gene coding for ubiquitin-activating enzyme UBE1, previously mapped in Xp11.3, indicating close physical linkage of these genes [16].
• This was demonstrated by inhibition of CD4 degradation (i) in cells expressing a thermally inactivated form of the ubiquitin-activating enzyme E1 or (ii) following expression of a mutant form of ubiquitin (Lys48 mutated to Arg48) known to compromise ubiquitin targeting by interfering with the formation of polyubiquitin complexes [17].

Other interactions of UBE1

• A homologue of UBE1, UBE1L, is located at 3p21 [18].
• We had previously generated a YAC contig in this region extending from UBE1 to the OATL1 locus [19].
• A novel gene, DXS8237E, lies within 20 kb upstream of UBE1 in Xp11.23 and has a different X inactivation status [20].
• These data enable the expansion of the present physical map of the X chromosome from UBE1 to the GATA locus, covering a large portion of the Xp11.23 region [19].
• For both markers the short arm breakpoints were localised between UBE1 and DXS423E [21].

Analytical, diagnostic and therapeutic context of UBE1

• Molecular cloning, primary structure and expression of the human X linked A1S9 gene cDNA which complements the ts A1S9 mouse L cell defect in DNA replication [5].
• Northern blot analysis of serum-starved, synchronized cells demonstrated that the A1S9 gene was expressed at a relatively low level in quiescent cells and at a higher and constant level throughout the cell cycle [5].
• Sequence analysis showed a 45% homology to the human ubiquitin-activating enzyme E1 at the amino acid level [22].
• Immunoblotting of eluates from GSH-Sepharose showed the presence of known (actin, ubiquitin-activating enzyme E1, NF-kappaB, and proteasome) and putative (p53, glutathione-S-transferase P1) targets for glutathionation [23].

References