LOW-TEMPERATURE ENHANCEMENT OF REPORTER GENES EXPRESSION DIRECTED BY HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 LONG TERMINAL REPEAT

Bacteria and eukaryotic cells respond to cold stress by inducing and e nhancing the synthesis of specific arrays of proteins. We describe her e cold-induced enhancement of expression for two reporter genes; lucif erase and beta-galactosidase, both under the control of HIV-1 LTR sequ ences, observed in mouse fibroblasts and human HeLa cells respectively . Increased expression of luciferase in fibroblasts when shifted to 25 degrees C was detectable at 30 degrees C but was not observed followi ng cold shock at 4 degrees C. To sustain the cold-induced effect, cell s had to be kept at subphysiological temperature. The observed enhance ment of luciferase activity did not result from a particular site of i ntegration of the reporter gene and was evident whether cold-stressed cells were stationary or growing. Cold-induced expression of luciferas e was evidenced at the protein level, enzymatic activity and RNA level , furthermore, active transcription and translation were required for overexpression. The cold effect which has been generalized with the re porter gene beta-galactosidase appears to be a process involving, at l east in part, the HIV-1 LTR sequences and might correspond to an Incre ase in the half-life of mRNA. The cold-dependent enhanced expression o f luciferase and beta-galactosidase reported here, together with data describing the activation of HIV-1 LTR by hyperthermia, point out the particular temperature sensitivity of these regulatory sequences. This potential thermal modulation may be useful in the comprehension of re gulatory processes in latency and reactivation of viral expression dur ing HIV-1 infection. (C) 1996 Academic Press, Inc.