TY - JOUR
T1 - Expression of exogenous Sam68, the 68-kilodalton Src-associated protein in mitosis, is able to alleviate impaired Rev function in astrocytes
AU - Li, Jinliang
AU - Liu, Ying
AU - Park, In Woo
AU - He, Johnny J.
PY - 2002
Y1 - 2002
N2 - Human immunodeficiency virus type 1 (HIV-1) gene expression in astrocytes is restricted, resulting in a brief and limited synthesis of HIV-1 viral structural proteins. Impaired Rev function has been documented in these cells. However, the molecular mechanisms underlying the impaired Rev function are not fully understood. Using the astroglial cell line U87.MG as a model, we report here that HIV-1 gene expression down-regulated expression of Sam68, the 68-kDa Src-associated protein in mitosis, which was constitutively expressed at a lower level in astrocytes. Elevating the endogenous level of Sam68 expression considerably restored HIV-1 Rev function in astrocytes, as determined by a Rev-dependent reporter gene assay. However, elevation of Sam68 expression achieved only a modest increase in HIV-1 production, further supporting the notion that there are multiple cellular restrictions of HIV-1 gene expression in astrocytes. Mutagenesis analysis identified the region between amino acids 321 and 410 of Sam68 as being directly involved in the binding of Sam68 to Rev, while a double mutation in Rev, L78D and E79L, like those in the dominant-negative Rev mutant M10, eliminated Rev binding to Sam68. Moreover, subcellular fractionation and digital fluorescence microscopic imaging revealed that Sam68 expression promoted Rev nuclear export. Taken together, our studies demonstrate that a lower level of constitutive Sam68 expression, followed by further down-regulation by HIV-1 infection, contributes to impaired Rev function in astrocytes, and they suggest that Sam68 may play an important role in Rev nuclear export.
AB - Human immunodeficiency virus type 1 (HIV-1) gene expression in astrocytes is restricted, resulting in a brief and limited synthesis of HIV-1 viral structural proteins. Impaired Rev function has been documented in these cells. However, the molecular mechanisms underlying the impaired Rev function are not fully understood. Using the astroglial cell line U87.MG as a model, we report here that HIV-1 gene expression down-regulated expression of Sam68, the 68-kDa Src-associated protein in mitosis, which was constitutively expressed at a lower level in astrocytes. Elevating the endogenous level of Sam68 expression considerably restored HIV-1 Rev function in astrocytes, as determined by a Rev-dependent reporter gene assay. However, elevation of Sam68 expression achieved only a modest increase in HIV-1 production, further supporting the notion that there are multiple cellular restrictions of HIV-1 gene expression in astrocytes. Mutagenesis analysis identified the region between amino acids 321 and 410 of Sam68 as being directly involved in the binding of Sam68 to Rev, while a double mutation in Rev, L78D and E79L, like those in the dominant-negative Rev mutant M10, eliminated Rev binding to Sam68. Moreover, subcellular fractionation and digital fluorescence microscopic imaging revealed that Sam68 expression promoted Rev nuclear export. Taken together, our studies demonstrate that a lower level of constitutive Sam68 expression, followed by further down-regulation by HIV-1 infection, contributes to impaired Rev function in astrocytes, and they suggest that Sam68 may play an important role in Rev nuclear export.
UR - http://www.scopus.com/inward/record.url?scp=0036223322&partnerID=8YFLogxK
U2 - 10.1128/JVI.76.9.4526-4535.2002
DO - 10.1128/JVI.76.9.4526-4535.2002
M3 - Article
C2 - 11932418
AN - SCOPUS:0036223322
SN - 0022-538X
VL - 76
SP - 4526
EP - 4535
JO - Journal of Virology
JF - Journal of Virology
IS - 9
ER -