The structure of HSAG-1, a middle repetitive genetic element which elicits a leukemia-related cellular surface antigen

HSAG-1 is a cloned member of a heterogeneous middle repetitive family of genetic elements which is capable of eliciting a leukemia-related surface antigen detected with a monoclonal antibody after DNA transformation of mouse cells. HSAG-1 was originally isolated from a Chinese hamster-human leukemia hybrid cell gene library both by sib-selection for antigen producing activity and by hybridization with labelled human genomic human DNA. We show here that the human labelled site is at the right hand end of the insert, while the antigen-eliciting portion is included in a 1450 bp fragment at the left hand end of the insert. We also present the complete nucleotide sequence of the 3369 bp insert. The sequence contains 12 elements which bear a significant resemblance to accepted consensus sequences for Alu repetitive elements. The right hand end contains adjacent elements with close sequence similarity to portions of the human and hamster type I and type II Alu consensus sequences. All of the other Alu-related elements have diverged relative to the Alu consensus sequences by additions, long deletions and substitutions. The left hand portion of the insert which has the antigen-producing activity contains four of these diverged elements representing a relatively high proportion (26%) of the nucleotide sequence. The sequence is thus consistent with our previous observations of a repetitive family with biological function.