PIWIL1/HIWI: ProductsPIWIL1 (piwi-like 1), also called HIWI (human homolog of drosophila piwi), is a cytoplasmic protein of the PIWI subgroup of the Argonaute family. PIWI domains bind a class of ~29-30 nucleotide RNAs termed piRNAs (piwi domain-binding RNAs). PIWIL1 orthologs are expressed with piRNAs in germ cells and are essential for spermatogenesis in mice. CD34+ hematopoietic progenitor cell PIWIL1 is downregulated upon differentiation. When overexpressed in leukemic cell lines, PIWIL1 inhibits growth and induces apoptosis.