Family With Sequence Similarity 158, Member B (FAM158B)

The NOC4 gene is located 5-prime to the COX4 gene in a head-to-head orientation. The transcription start sites of the 2 genes are within 250 bp of each other. A human retinal NOC4 cDNA encoded a predicted 210-amino acid protein containing a putative transmembrane domain. The NOC4 protein did not share sequence similarity with known proteins. Recombinant NOC4 protein expressed in HeLa cells was located in both the nucleus and the cytoplasm, including the mitochondria. Northern blot analysis detected 2.2- and 1.4-kb NOC4 transcripts in all adult human tissues tested, namely liver, pancreas, heart, lung, kidney, brain, skeletal muscle, and placenta. NOC4 expression levels were highest in pancreas and moderate in heart, skeletal muscle, and placenta. The expression levels of NOC4 and COX4 varied concordantly in different tissues.