Chromosoma (1991) 100 : 118 124 CHROMOSOMA 9 Springer-Verlag199l He-T family DNA sequences in the Y chromosome of Drosophila melanogaster share homology with the X-linked Stellate genes Olga N. Danilevskaya 1,2, Elena V. Kurenova 2 Maria N. Pavlova 2, Dmitrii V. Bebehov 2, Andrew J. Link 3, Akihiko Koga 1, Ann Vellek 1, and Daniel L. Hartl 1 1 Department of Genetics, Washington University School of Medicine, St. Louis, MO 63110-1095, USA 2 Institute of Molecular Genetics, USSR Academy of Sciences, 123182 Moscow, USSR 3 Department of Genetics, Harvard Medical School, Boston, MA 02115, USA Received August 15, 1990 Accepted August 28, 1990 by W. Hennig Abstract. The genome of Drosophila melanogaster con- tains a class of repetitive DNA sequences called the He-T family, which is unusual in being confined to telomeric and heterochromatic regions. The specific He-T frag- ment designated Dm665 was cloned in yeast by selection for an autonomously replicating sequence (ARS). Dm665 contains a restriction fragment length polymor- phism (RFLP) that is specific to males and thus derives from the Y chromosome. Deletion mapping using J(-Y translocations indicates that sequences homologous to Dm665 occur in at least one major cluster in each arm of the Y chromosome. Among 20 yeast artificial chro- mosome (YAC) clones containing Drosophila sequences homologous with Dm665, four clones derive from de- fined regions of the long arm of the Y and two from the short arm. The sequence of Dm665 is 2443 bp long, consists of 59% A+T, and contains no significant open reading frames or direct or inverted repeats. However, Dm665 contains a region of 650 bp that shares homolo- gy with portions of the X-linked locus Stellate. chromosomes indicate that He-T sequences are abun- dant in the Y chromosome (Traverse and Pardue 1989). We have studied a Drosophila DNA fragment, desig- nated Dm665, that confers the ability to replicate auton- omously on a plasmid of Saccharomyces cerevisiae. This fragment hybridizes in situ with the tips of the Drosophi- la polytene chromosomes and with the chromocenter, the region in which the relatively underreplicated hetero- chromatin of the salivary gland chromosomes is concen- trated (Danilevskaya et al. 1984). The Dm665 fragment is homologous to the He-T family and contains a restric- tion fragment length polymorphism (RFLP) specific to the Y chromosome. The nucleotide sequence of this Y chromosome fragment is relatively A + T rich and con- tains no significant open reading frames or repeated se- quences. RFLPs specific to the Y chromosome have en- abled physical localization of homologous He-T se- quences in both arms of the Y and the isolation of yeast artificial chromosomes (YACs) containing Drosophila DNA sequences that derive from these regions of the Y chromosome. Introduction The pericentromeric regions of the chromosomes of Dro- sophila melanogaster, and the entirety of the Y chromo- some, consist of heterochromatin, different blocks of which are composed of 30%-70% highly repetitive, tan- demly repeated, simple sequence, "satellite" DNA (Miklos 1985). This is interrupted at irregular intervals by unique DNA sequences and moderately repetitive se- quences of various kinds (Young et al. 1983; Shevelyov et al. 1989). Among the moderately repetitive sequences are those referred to as the He-T family (Traverse and Pardue 1989), owing to their occurrence in both hetero- chromatic and telomeric regions (Rubin 1978; Traverse and Pardue 1989; Renkawitz-Pohl and Bialojan 1984). DNA hybridizations carried out in situ with metaphase Offprint requests to ." D.L. Hartl Materials and methods Drosophila strains. All plasmid, phage, and YAC clones originate from the Drosophila strain Oregon RC. Strains of D. melanogaster carrying X- Y translocations used for localization of sequences ho- mologous to Dm665 are described in Hardy et al. (1981). Plasmids and hosts. Plasmid p665-52 was obtained by subcloning the Dm665 HindIII fragment from yeast plasmid p665 into the yeast vector YIp5 as described in Danilevskaya et al. (1984). Re- combinant pBR322 clones were prepared from BamHI or PstI di- gested DNA of Drosophila adults and transformed into bacterial recipient strains DH5~ or HB101 (Sambrook et al. 1989). YAC clones'. Gastrula cells from the Oregon RC strain were washed in Hank's balanced salt solution at 4~ C, centrifuged, and resus- pended to a concentration of 9 x 108 cells/ml. Dilutions of 0.05 0.1 ml were warmed to 25~ C, mixed with 1% low melting tempera- ture agarose (Sigma) in 1 M NaCI, 10 mM Tris, pH 7.5, in a ratio of cell suspension:agarose of 4:5 (v/v) and aliquots transferred