THE ACIDIC DOMAIN OF THE HUMAN CYTOMEGALOVIRUS UL37 IMMEDIATE-EARLY GLYCOPROTEIN IS DISPENSABLE FOR ITS TRANSACTIVATING ACTIVITY AND LOCALIZATION BUT IS NOT FOR ITS SYNERGISM
Hz. Zhang et al., THE ACIDIC DOMAIN OF THE HUMAN CYTOMEGALOVIRUS UL37 IMMEDIATE-EARLY GLYCOPROTEIN IS DISPENSABLE FOR ITS TRANSACTIVATING ACTIVITY AND LOCALIZATION BUT IS NOT FOR ITS SYNERGISM, Virology, 223(2), 1996, pp. 292-302
The product of the human cytomegalovirus (HCMV) immediate early (IE) U
L37 gene, gpUL37, is predicted to he a type I membrane-bound glycoprot
ein. Typically for HCMV IE proteins, gpUL37 transactivates nuclear gen
e expression and acts synergistically with other IE proteins. We have
initiated mutational analysis of the gpUL37 domains to determine which
are required for its transactivating activity. The acidic domain, a f
eature notably required for the activity of many nuclear transcription
factors, was deleted from gpUL37. Similar to wild-type gpUL37, the mu
tant retained a dose responsive transactivating activity in transientl
y transfected HeLa cells. Transactivating activity of the mutant was a
lso observed in permissive human diploid fibroblasts when it was cotra
nsfected with IE1. However, the gpUL37 acidic domain mutant is defecti
ve for synergism with another HCMV 1E protein, puss. We found that wil
d-type gpUL37 and its acidic domain mutant (Delta aa53-140) are nonnuc
lear proteins and are indistinguishable in localization. Confocal micr
oscopy of human cell types coexpressing both HCMV IE regulatory protei
ns, IE1 and gpUL37, showed gpUL37 does not colocalize with the IE1 nuc
lear protein. Taken together, our results establish that gpUL37 is a n
onnuclear protein that requires its acidic domain for synergism with p
US3 but not for its transactivating activity or its localization. (C)
1996 Academic Pleas, Inc.