The HIV-1 Tat protein regulates transcription elongation through binding to the viral TAR RNA stem-loop structure. We have isolated a novel 87 kDa cyclin C-related protein (cyclin T) that interacts specifically with the transactivation domain of Tat. Cyclin T is a partner for CDK9, an RNAPII transcription elongation factor. Remarkably, the interaction of Tat with cyclin T strongly enhances the affinity and specificity of the Tat:TAR RNA interaction, and confers a requirement for sequences in the loop of TAR that are not recognized by Tat alone. Moreover, overexpression of human cyclin T rescues Tat activity in nonpermissive rodent cells. We propose that Tat directs cyclin T-CDK9 to RNAPII through cooperative binding to TAR RNA.

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A series of novel cationic gemini surfactants [C n H 2n?1 -O-CH 2 -CH(OH)-CH 2 -N ? (CH 3 ) 2 -(CH 2 ) 2 ] 2 Á2Br -[3a (n = 12), 3b (n = 14) and 3c (n = 16)] having a 2-hydroxy-1,3-oxypropylene group [-CH 2 -CH(OH)-CH 2 -O-] in the hydrophobic chain have been synthesized and characterized. Their water solubility, surface activity, foaming properties, and antibacterial activity have been examined. The critical micelle concentration (CMC) values of the novel cationic gemini surfactants are one to two orders of magnitude smaller than those of the corresponding monomeric surfactants. Furthermore, the novel cationic gemini surfactants have better water solubility and surface activity than the comparable [C n H 2n?1 -N ? (CH 3 ) 2 -(CH 2 ) 2 ] 2 Á2Br -(n-4-n) geminis. The novel cationic gemini surfactants 3a and 3b also exhibit good foaming properties and show good antibacterial and antifungal activities.

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