This region of these proteins has been suggested to be homologous to acetyltransferases [1].

1: Identification of a cellular protein that specifically interacts with the essential cysteine region of the HIV-1 Tat transactivator. Kamine J, Elangovan B, Subramanian T, Coleman D, Chinnadurai G; Virology 1996;216:357-366. PMID:8607265

2: Yeast SAS silencing genes and human genes associated with AML and HIV-1 Tat interactions are homologous with acetyltransferases [see comments] [published erratum appears in Nat Genet 1997 May;16(1):109] Reifsnyder C, Lowell J, Clarke A, Pillus L; Nat Genet 1996;14:42-49. PMID:8782818