Suggested positive control: antigen standard for NOL3 (transient overexpression lysate). Nop30 (nucleolar protein of 30 kDa) is predominantly expressed in muscle and is present in the nucleoplasm and concentrated in nucleoli. The predominant nucleolar localization of Nop30 points to a potential role in RNA processing in muscle nucleoli. A CARD domain containing protein, designated ARC for apoptosis repressor with CARD is related to Nop30 with a different carboxyl terminus.