Involved in the earliest step for the formation of the active cleavage complex, the CFIm complex is formed by three proteins of 25, 59 and 68 kDa, respectively:
*CFIm25 (or CPSF5/NUDT21)
*CFIm59 (or CPSF7)
*CFIm68 (or CPSF6)
CFIm25 and CFIm68 are sufficient for the activity of the complex, proving the expected redundancy of CFIm68 and CFIm59, which share great sequence similarity.