Shows no ribosome-associated and endoribonuclease activities. Displays polysome-associated endoribonuclease activity towards mRNAs and rRNAs (PubMed:25996083). May play a role in RNA surveillance pathways by recognizing stalled ribosomes and triggering endonucleolytic cleavage of aberrant mRNAs (Probable). Cleaves different types of rRNAs and mRNAs in a magnesium- and manganese-dependent and ATP-independent manner (By similarity). Involved in correct maturation of megakaryocytes and especially important for proplatelet extension. C-terminally truncated SLFN14 endoribonuclease requires manganese and magnesium for its endoribonuclease activity. Associates with ribosomes in an ATP-independent manner (PubMed:25996083). Expressed in megakaryocytes and platelets (at protein level) (PubMed:26280575). Weakly expressed in melanocytes and malignant melanoma cells (PubMed:20956525). The disease is caused by variants affecting the gene represented in this entry. Belongs to the Schlafen family. Subgroup III subfamily.