The yeast Pop2 protein, belonging to the eukaryotic Caf1 family, is required for 
mRNA deadenylation in vivo. It also catalyzes poly(A) degradation in vitro, even 
though this property has been questioned. Caf1 proteins are related to RNase D, 
a feature supported by the recently published structure of Pop2. Yeast Pop2 
contains, however, a divergent active site while its human homologs harbor 
consensus catalytic residues. Given these differences, we tested whether its 
deadenylase activity is conserved in the human homologs Caf1 and Pop2. Our data 
demonstrate that both human factors degrade poly(A) tails indicating their 
involvement in mRNA metabolism.