some with respect to X inactivation. This presum- 
ably results from selection for the active normal X 
during B cell differentiation. Dr. Belmont's labora- 
tory has developed a highly informative PCR-based 
assay for carrier detection, using differential methyl- 
ation of Hpall and Hhal sites near the polymorphic 
CAG repeat in the androgen receptor locus. 
Dr. Belmont is also Assistant Professor in the 
Institute for Molecular Genetics, Department of 
Microbiology and Immunology, and Department 
of Pediatrics at Baylor College of Medicine and a 
member of the staff at Texas Children's Hospital 
and Ben Taub General Hospital, Houston. 
Articles 
Allen, R.C., and Belmont, J.W. 1992. Dinucleotide 
repeat polymorphism at the DXS178 locus. Hum 
Mol Genet 1(3):216. 
Claxton, D., Suh, S.-P., Filaccio, M., Ellerson, D., 
Gaozza, E., Anderson, B., Brenner, M., Reading, 
C., Feinberg, A., Moen, R., Belmont, J., Moore, 
K., Talpaz, M., Kantarjian, H., and Deisseroth, A. 
1991. Molecular analysis of retroviral transduc- 
tion in chronic myelogenous leukemia. Hum 
Gene Ther 2:317-321 . 
Cournoyer, D., Scarpa, M., Mitani, K., Moore, K.A., 
Markowitz, D., Bank, A., Belmont, J.W., and Cas- 
key, C.T. 1991. Gene transfer of adenosine deami- 
nase into primitive human hematopoietic progen- 
itor cells. Hum Gene Ther 2:203-213. 
Etkin, M., Filaccio, M., Ellerson, D., Suh, S.-P., Clax- 
ton, D., Gaozza, E., Brenner, M., Moen, R., Bel- 
mont, J., Moore, K.A., Moseley, A.M., Reading, 
C., Khouri, I., Talpaz, M., Kantarjian, H., and 
Deisseroth, A. 1992. Use of cell-free retroviral 
vector preparations for transduction of cells from 
the marrow of chronic phase and blast crisis 
chronic myelogenous leukemia patients and from 
normal individuals. Hum Gene Ther 3:157-145. 
Fletcher, F.A., and Belmont, J.W. 1991. Stimula- 
tion of retroviral vector infection of murine hema- 
topoietic progenitors. Int J Cell Cloning 9:491- 
502. 
Fletcher, F.A., Moore, K.A., Ashkenazi, M., De Vries, 
P., Overbeek, P.A., Williams, D.E., and Bel- 
mont, J.W. 1991. Leukemia inhibitory factor im- 
proves survival of retroviral vector-infected hema- 
topoietic stem cells in vitro, allowing efficient 
long-term expression of vector-encoded human 
adenosine deaminase in vivo. J Exp Med 
174:837-845. 
Moore, K.A., Deisseroth, A.B., Reading, C.L., Wil- 
liams, D.E., and Belmont, J.W. 1992. Stromal 
support enhances cell-free retroviral vector trans- 
duction of human bone marrow long-term cul- 
ture-initiating cells, fi/oorf 79:1393-1399- 
Moore, K.A., Scarpa, M., Kooyer, S., Utter, A., Cas- 
key, C.T., and Belmont, J.W. 1991. Evaluation 
of lymphoid-specific enhancer addition or substi- 
tution in a basic retrovirus vector. Hum Gene 
Ther 2:507-515. 
Reichardt, J.K.V., Belmont, J.W., Levy, H.L., and 
Woo, S.L.C. 1992. Characterization of two mis- 
sense mutations in human galactose- 1 -phosphate 
uridyltransferase: different molecular mecha- 
nisms for galactosemia. Genomics 12:596-600. 
RETROVIRAL REPLICATION AND NEW METHODS FOR GENE MAPPING 
Patrick O. Brown, M.D., Ph.D., Assistant Investigator 
Retroviral Replication 
Dr. Brown's laboratory is studying the mechanism 
by which a retrovirus delivers its genome into the 
nucleus of the infected cell and integrates the viral 
DNA molecule into a host cell chromosome. These 
steps are essential for retroviral replication. Retro- 
viral integration provides a uniquely efficient means 
of inserting foreign DNA into mammalian chromo- 
somes and thus can play a key role in genetic engi- 
neering and gene therapy. Moreover, since integra- 
tion depends on virally encoded functions and has 
no known essential cellular counterpart, it provides 
a promising target for development of new antiviral 
agents. Two retroviruses are being studied in Dr. 
Brown's laboratory, the Moloney murine leukemia 
virus (MLV) and the human immunodeficiency 
virus (HFV). 
Using an Escherichia coli expression system, 
postdoctoral fellows Drs. Samson Chow, Iris Dotan, 
and Karen Vincent and graduate students Viola Elli- 
son and Brian Scottoline have prepared and purified 
milligram quantities of the wild-type HIV and MLV 
integrase proteins, as well as several mutant versions 
of HIV integrase. The integrase proteins have several 
activities that can be independently assayed, includ- 
ing sequence-specific endonucleolytic processing 
160 
