Characterization of TRBP1 and TRBP2 - Stable stem-loop structure at the 5 ' end of TRBP2 mRNA resembles HIV-1 TAR and is not found in its processed pseudogene

TRBP1 and TRBP2 cDNAs have been isolated based on the ability of the protei n that they encode to bind HIV-1 TAR RNA. The two cDNAs have different 5' e nd-termini resulting in 21 additional amino acids for TRBP2 protein compare d to TRBP1, The corresponding gene is conserved in mammalian species, By PC R amplification of a human library, we have isolated an additional 22 nucle otides in the 5' end of TRBP2 cDNA, Based on the addition of these 22 new n ucleotides, the first 87 nucleotides of TRBP2 mRNA can fold into a stable s tem-loop structure that resembles TAR RNA. We have also isolated the DNA se quence that represents the TRBP processed pseudogene. The absence of full a lignment between TRBP2 full-length cDNA and this sequence suggests that the stem-loop structure could have prevented a complete reverse transcription during pseudogene formation. Using different antibodies, three forms of TRB P can be identified in primate cells at 40, 43 and 50 kD, suggesting a diff erential expression from the cDNAs and post-translational modifications. Bo th TRBP1 and TRBP2 activate the basal and the Tat-activated level of the HI V-1 LTR in human and murine cells. Our data indicate that TRBP proteins act at a level prior to Tat function, TRBP could contribute to improved HIV ex pression in murine models. Copyright (C) 2000 National Science Council, ROC and S. Karger As. Basel.