KRR1 encodes a small subunit processome component essential for ribosomal biogenesis. KRR1 localizes to the nucleolus and functions as a structural and catalytic component of the 90S pre-ribosome assembly complex 1. The protein coordinates early assembly events by working with the snoRNP complex snR30 and co-factors Utp23 and Kri1 to recruit ribosomal proteins and facilitate folding of the 40S central domain platform 2. KRR1 is essential for 18S rRNA processing and 40S ribosomal subunit maturation; depletion causes drastic reduction in functional 40S subunits due to defective pre-rRNA synthesis 1. The gene shows high expression in actively dividing cells, where efficient ribosome biogenesis is critical for translation capacity 3. Beyond its housekeeping ribosomal function, KRR1 has disease relevance: genetic variants at the KRR1 locus (rs1275468, 12q21.2) were identified in genome-wide association studies as potential susceptibility factors for polycystic ovary syndrome, though confirmation in non-European populations remains incomplete 4. Additionally, KRR1 is recognized as a tumor-associated autoantigen with elevated antibody response in breast cancer patients 5. The protein's conservation from primitive eukaryotes to humans underscores its fundamental role in cellular viability.