SPEM1 is a 309 amino acid transmembrane and cytoplasmic protein that is required for proper cytoplasm removal during spermatogenesis. SPEM1 interacts with both Ran BP-17 and PLIC-1. Since PLIC-1 functions through binding and directing poly-ubiquitinated proteins to the proteasome for degradation, interactions between PLIC-1 and SPEM1 suggest a role in the regulation of protein ubiquitination during spermiogenesis. The SPEM1 gene maps to human chromosome 17p13.1. Comprising over 2.5% of the human genome, chromosome 17 consists of about 81 million bases, encodes over 1,200 genes and has the highest gene density in the genome. Chromosome 17 is also enriched in segmental duplications, ranking third in density among the autosomes.