The testis specific variant of the RNA polymerase-associated factor 1 complex (tPAF) is composed of testis-specific paralog proteins of each of the four canonical PAF1 complex core proteins. Unlike the canonical complex, it has not been shown to associate with an Rtf1 family protein (FBrf0260702). Additionally, unlike the other genes encoding members of tPAF complex, the testis-specific Rtf1 paralog, Rtf1L, mutants showed no fertility defects, and Rtf1L did not colocalize with or coimmunoprecipitate tPAF proteins (FBrf0260702). FBrf0263025 suggests that Rtf1L is a component of tPAF by expression pattern, but does not test this and so is not included as a component of the gene group. Ski8 was shown to coimmunoprecipitate and colocalized tPAF (FBrf0260702). In the human PAF1 complex Ski8 is also part of canonical PAF1C (PMID:16024656).