THE S. /.A.IG AMINO-ACID MOTIF IS PRESENT IN A REPLICATION DEPENDENT LATE H3 HISTONE VARIANT OF P-LIVIDUS SEA-URCHIN/

A novel gene encoding a new H3 histone variant (H3L) has been identifi ed in P, lividus sea urchin embryo, It encodes a H3 histone protein sh owing the S.//A.IG amino acid motif typical of the replication indepen dent H3.3 variants but in a mRNA showing the 3' terminal stem-loop nuc leotide sequence that is typical of the replication dependent variants . The gene is intronless, the corresponding short transcript is non-po lyadenylated and its expression is replication dependent with a timing of a late variant. The new H3 variant is expressed as a minor compone nt with respect to a major replication dependent late H3 histone here identified by partial cDNA sequence, These results show that classific ation of histones in replication dependent and independent variants on ly on the basis of their amino acid sequences should be reconsidered. (C) 1997 Federation of European Biochemical Societies.