CRYSTAL-STRUCTURE OF THE 2 RNA-BINDING DOMAINS OF HUMAN HNRNP A1 AT 1.75 ANGSTROM RESOLUTION

Heterogeneous ribonucleoprotein Al (hnRNP Al) is an abundant eukaryoti c nuclear RNA binding protein. Al is involved in the packaging of pre- mRNA into hnRNP particles, transport of poly A(+) mRNA from the nucleu s to the cyto plasm and may modulate splice site selection. The crysta l structure of A1(RBD1,2) reveals two independently-folded RNA binding domains (RBDs) connected by a flexible linker. Both RBDs are structur ally homologous to the U1A(RBD1), and have their RNA binding platforms oriented in an anti-parallel fashion. The anti-parallel arrangement o f the Al RNA binding platforms suggests mechanisms for RNA condensatio n and ways of bringing together distant RNA sequences for RNA metaboli sm such as splicing or transport.