We report here the molecular cloning of an Ϸ1-Mb region of recurrent amplification at 20q13.2 in breast cancer and other tumors and the delineation of a 260-kb common region of amplification. Analysis of the 1-Mb region produced evidence for five genes, ZNF217, ZNF218, and NABC1, PIC1L (PIC1-like), CYP24, and a pseudogene CRP (Cyclophillin Related Pseudogene). ZNF217 and NABC1 emerged as strong candidate oncogenes and were characterized in detail. NABC1 is predicted to encode a 585-aa protein of unknown function and is overexpressed in most but not all breast cancer cell lines in which it was amplified. ZNF217 is centrally located in the 260-kb common region of amplification, transcribed in multiple normal tissues, and overexpressed in all cell lines and tumors in which it is amplified and in two in which it is not. ZNF217 is predicted to encode alternately spliced, Kruppel-like transcription factors of 1,062 and 1,108 aa, each having a DNA-binding domain (eight C2H2 zinc fingers) and a proline-rich transcription activation domain.Studies in which comparative genomic hybridization was used have revealed Ϸ20 regions of recurrent increased DNA sequence copy number in breast tumors (1-3). These regions are predicted to encode dominantly acting genes that may play a role in tumor progression or response to therapy. To date, three of these regions have been associated with established oncogenes: ERBB2 at 17q12, MYC at 8q24, and CCND1 and EMS1 at 11q13. In breast cancer, ERBB2 and CCND1͞EMS1 amplification and overexpression are associated with decreased life expectancy (4, 5), whereas MYC amplification has been associated with lymph node involvement, advanced stage, and an increased rate of relapse (6, 7). Efforts are now underway in several laboratories to identify oncogenes in the other regions of amplification.Amplification at 20q13 is particularly interesting because this aberration occurs in a variety of tumor types and is associated with aggressive tumor behavior. The initial comparative genomic hybridization study showed increased copy number involving 20q13 in 40% of breast cancer cell lines and 18% of primary breast tumors (2). Since then, other comparative genomic hybridization studies have revealed copynumber gains at 20q13 in greater than 25% of cancers of the ovary (8), colon (9), head and neck (10

Alu repetitive elements represent the most common short interspersed elements (SINEs) found in primates, with an estimated 500,000 members in the haploid human genome. Considerable evidence has accumulated that these elements have dispersed in the genome by active transcription followed by retroposition, and that this process is ongoing. Sequence variation between the individual elements has lead to the hierarchical classification of Alu repeats into families and subfamilies. Young subfamilies that are still being actively transposed are of considerable interest, and the identification of one such subfamily (designated 'PV') has lead to the hypothesis that the most recent retroposition events are due to a single master Alu source gene. In the course of our search for the gene causing Huntington disease, we have detected an Alu retroposition event in two families. Sequence analysis demonstrates that this Alu element is not a member of the PV subfamily, but is similar to 5 other Alu elements in the GenBank database. Together, these Alu elements, all of which contain a 7 base-pair internal duplication, define a distinct subfamily, designated as the Sb2 subfamily, providing evidence for a second actively retroposing Alu source gene. These data provide support for multiple source genes for Alu retroposition in the human genome.