Alu sequences are frequently encountered during study of human genomic
nucleic acid and form a major component of repetitive DNA. This revie
w describes the origin of Alu sequences and their subsequent amplifica
tion and evolution into distinct subfamilies, In recent years a number
of different functional roles for Alu sequences have been described,
The multiple influences of Alu sequences on RNA polymerase II-mediated
gene expression and the presence of Alu sequences in RNA polymerase I
II-generated transcripts are discussed. (C) 1997 Federation of Europea
n Biochemical Societies.