Journal of Virology, August 2000, p. 7179-7186, Vol. 74, No. 15
RIKEN Tsukuba Institute, Tsukuba, Ibaraki
305-0074, Japan
Received 24 February 2000/Accepted 8 May 2000
To identify the domains of Vpr that are involved nuclear
localization, we transfected HeLa cells with a panel of expression vectors that encode mutant Vpr protein with deletions or substitutions within putative domains. Immunofluorescence staining of transfected cells revealed that wild-type Vpr was localized predominantly in the
nucleus and the nuclear envelope and certainly in the cytoplasm. Introduction of substitutions or deletions within
0022-538X/00/$04.00+0
Two Putative
-Helical Domains of Human
Immunodeficiency Virus Type 1 Vpr Mediate Nuclear Localization by
at Least Two Mechanisms
H1 or
H2
resulted, by contrast, in diffuse expression over the entire cell. In
addition, double mutations within both of these
-helical domains led
to the complete absence of Vpr from nuclei. Next, we prepared HeLa cells that express chimeric proteins which consist of the
H1 and
H2 domains fused individually with green fluorescent protein (GFP)
and a Flag tag and extracted them with digitonin and Triton X-100 prior
to fixation. Flag-
H1-GFP was detected in the nucleus but not in the
cytoplasm, while Flag-
H2-GFP was retained predominantly in the
nucleus and in a small amount in the cytoplasm. The immunostaining patterns were almost eliminated by substitutions in each chimeric protein. Thus, it appeared that the two
-helical domains might be
involved in nuclear import by binding to certain cellular factors. Taken together, our data suggest that the two putative
-helical domains mediate the nuclear localization of Vpr by at least two mechanisms.
*
Corresponding author. Mailing address: RIKEN Tsukuba
Institute, 3-1-1 Koyadai, Tsukuba, Ibaraki 305-0074, Japan. Phone: 81 298 36 3522. Fax: 81 298 36 9050. E-mail:
aida{at}rtc.riken.go.jp.
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