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J. Virol., 10 1996, 7198-7208, Vol 70, No. 10
HO Al-Barazi and AM Colberg-Poley
The human cytomegalovirus (HCMV) UL37 immediate-early gene is predicted to
encode a type I membrane-bound glycoprotein, gpUL37. Following expression
of the UL37 open reading frame in vitro, its signals for translocation and
N-glycosylation were recognized by microsomal enzymes. Its orientation in
the microsomes is that of a type I protein. gpUL37 produced in
HCMV-infected human cells was selectively immunoprecipitated by rabbit
polyvalent antiserum generated against the predicted unique domains of the
UL37 open reading frame and migrated as an 83- to 85-kDa protein.
Tunicamycin treatment, which inhibits N- glycosylation, increased the rate
of migration of the UL37 protein to 68 kDa, verifying its modification by
N-glycosylation in HCMV-infected cells. Consistent with this observation,
gpUL37 was found to be resistant to digestion with either endoglycosidase F
or H but sensitive to peptide N-glycosidase F digestion. These results
suggested that gpUL37 is N-glycosylated and processed in both the
endoplasmic reticulum (ER) and the Golgi apparatus. Direct demonstration of
passage of gpUL37 through the ER and the Golgi was obtained by confocal
microscopy. gpUL37 colocalized with protein disulfide isomerase, a protein
resident in the ER, and with a Golgi protein. Subcellular fractionation of
HCMV-infected cells demonstrated that gpUL37 is an integral membrane
protein. Taken together, our results demonstrate that the HCMV gpUL37
immediate-early regulatory protein is a type I integral membrane
N-glycoprotein which traffics through the ER and the Golgi network.
Copyright © 1996, American Society for Microbiology
The human cytomegalovirus UL37 immediate-early regulatory protein is an integral membrane N-glycoprotein which traffics through the endoplasmic reticulum and Golgi apparatus
Center for Virology, Immunology and Infectious Disease Research, Children's National Medical Center, Washington, DC 20010, USA.
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