Knockdown of CPSF5 (CFIm25) or CPSF6 (CFIm68), two key subunits of the CFIm tetramer leads to a widespread increase in the use of proximal PASs (pPASs) [40], making this complex a key candidate to reveal the genome-wide landscape of shortened tandem 3’ UTRs upon viral infection. Here, NUDT21 is linked to viral infectious disease.