Figure 1.—

The Drosophila nocturnin (curled) gene: gene locus organization, deletion mutants, and phylogeny of Nocturnin proteins. (A) Organization of nocturnin (curled) gene locus with transcript isoforms no(cu)-RC, no(cu)-RD, and no(cu)-RE relative to the flanking genes CG18577 and SdhC at 86D7 on chromosome 3R. [Note: Coding parts of exons are marked by black, noncoding parts by white boxes; hatched boxes, Mg²⁺-dependent endonuclease-like domain (pfam03372); no(cu)-RC, -RD, -RE are the only no(cu) transcripts annotated in FlyBase r5.17.] Transposon integration line P{EP}no(cu)^GE22476 was used to generate nocturnin (curled) deletion mutants no¹ (cu³), no² (cu⁴), and no³ (cu⁵) as well as genetically matched no⁺ (cu⁺) control line no(cu)^GE22476rv. (B) Sequence alignment of vertebrate und invertebrate Nocturnin (NO) protein family members proves strong evolutionary conservation of amino acids involved in the catalytic function of yCCR4-related family proteins (amino acids identical to D. melanogaster NO are shaded in gray). Residues essential for the Mg²⁺-dependent endonuclease-like domain function are indicated as in Dupressoir et al. (2001): ▵, catalytic residue; □, residues involved in orientation and stabilization of catalytic residues; ○, for phosphate binding, and •, for Mg²⁺ binding residues; #, position of stop in no^stop12.2. The black bar illustrates the extent of the pfam03372 domain. (C) Phylogenetic tree analysis showing that Drosophila NO(CU) is the Nocturnin ortholog (Nocturnin subfamily shaded gray) among the four yCCR4-related proteins of the fly. (D) Northern blot analysis of adult flies shows nocturnin (curled) small S and large L transcript populations in no(cu)^GE22476rv controls and identifies no¹ (cu³) as transcript null mutation. No³ (cu⁵) specifically lacks no(cu) L transcripts, while no² (cu⁴) expresses a low abundance transcript slightly shorter than the no(cu) S transcript of control flies. SdhC transcript is unaffected in all no(cu) mutants. (E) Distally upward bent wing (left panel) and proximally crossed posterior scutellar bristle (right panel) phenotypes of no¹ (cu³) mutants compared to no(cu)^GE22476rv controls.