1904502 SECIS Sec insertion sequence 59 1904507 SECIS selenocysteine insertion sequence 5 1904503 SECIS selenocysteine insertion 4 1904501 SECIS Sec insertion sequence element 3 1904505 SECIS selenocysteine insertion element 2 1904504 SECIS secondary structure in the mRNA 1 1904506 SECIS special cis-acting Sec insertion sequence 1 1904508 SECIS structure, called selenocysteine insertion sequence 1