INCORPORATION OF NUCLEAR MATRIX ATTACHMENT REGIONS INTO THE HERPES-SIMPLEX VIRUS TYPE-1 GENOME DOES NOT INDUCE LONG-TERM EXPRESSION OF A FOREIGN GENE DURING LATENCY

The nuclear matrix plays a critical role in DNA replication, gene tran scription and RNA processing. Transcriptionally active genes are usual ly associated with the nuclear matrix through DNA sequences, matrix at tachment regions or MARs which tether leaped DNA to the matrix. in sta ble transfection and in transgenic mice MAR elements placed at the fla nks of genic constructs may enhance expression and insulate against po sition effect variability, suggesting that independent units of transc ription are established insulated from the regulatory controls of thei r neighbors. Herpes simplex virus type 1 (HSV-1) establishes lifelong latency in the infected host Latency repression of viral genes extends to foreign genes incorporated into the viral genome. We report here a test of the hypothesis that MAR elements, flanking a foreign gene in the HSV-1 genome, would act to insulate if from latency repression, ac hieving long-term expression. A recombinant virus was produced which h as an expression construct inserted into the HSV-1 genome at the U(S)3 locus. The expression construct consists of the A MAR element on one flank, an HIV-LRT driving the lacZ gene and the B MAR element on the o ther flank. The A MAR element is a 3 kb pair fragment of the 5' portio n of the chicken lysozyme gene and the B MAR element is a 2.6 kb pair fragment from the 5' end of the human beta-globin gene locus control r egion, The LTR is derived from a human immunodeficiency virus isolated from the brain of an AIDS patient. Virus was stereotactically injecte d in the hippocampus, olfactory bulb and striatum of rat brains. inten se blue reaction product indicating beta-galactosidase activity was fo und in cells in each injected area at 2 days after injection. At 14 da ys after injection beta-galactosidase activity was no longer detected at any of the injected sites. We conclude that the MAR element constru ct did not escape latency repression.