Linked Life Data

8663123

Source:http://linkedlifedata.com/resource/pubmed/id/8663123

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
26
pubmed:dateCreated
1996-8-20
pubmed:abstractText
The ubiquitin-activating enzyme E1 exists as two isoforms, E1a (117 kDa) and E1b (110 kDa). E1a is phosphorylated, whereas E1b is not. In the present study we have demonstrated the cell cycle dependence of E1a phosphorylation: a 2-fold increase in the specific phosphorylation of E1a in G2 compared with the basal level of phosphorylation in the other stages of the cell cycle. Two-dimensional gel electrophoresis resolved E1 into the two isoforms E1a and E1b; E1a resolved further as three phosphorylated forms and one nonphosphorylated form, while E1b resolved as one nonphosphorylated form. E1a is found predominantly in the phosphorylated forms. However, the distribution of E1a among these different phosphorylated forms was not cell cycle-dependent. We next evaluated the enzymatic activity of E1 as well as its subcellular localization throughout the cell cycle. 32P-Pyrophosphate exchange activity of E1 did not vary along the cell cycle; however, the amount of ubiquitin-protein conjugates decreased by 50% in G2. Nuclear and cytosolic fractionation of cells revealed the nuclear to cytosolic ratio of phosphorylated E1a was 3-fold greater in G2 compared with the other stages of the cell cycle. Finally, purified nuclear extracts supported E1-dependent ubiquitin conjugation of exogenous substrates as did purified cytosol. However, in nuclear extracts but not in cytosol the amount of E1 activity was rate-limiting. Thus we establish nuclear E1-dependent protein ubiquitination and propose that an increase in phosphorylation of E1a in G2 functions to increase the import and/or retention of E1a in the nucleus and may modulate nuclear protein ubiquitination.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jun
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
28
pubmed:volume
271
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
15608-14
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1996
pubmed:articleTitle
The ubiquitin-activating enzyme E1 is phosphorylated and localized to the nucleus in a cell cycle-dependent manner.
pubmed:affiliation
Edward Mallincrodt Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.