Elsevier

Gene

Volume 231, Issues 1–2, 29 April 1999, Pages 173-186
Gene

The Drosophila STAM gene homolog is in a tight gene cluster, and its expression correlates to that of the adjacent gene ial

https://doi.org/10.1016/S0378-1119(99)00053-0Get rights and content

Abstract

Drosophila STAM is a homolog of mammalian STAM genes, which encode Jak associated signal-transducing adapter molecules. A 20-kilobase stretch of genomic DNA at 32B on chromosome arm 2L, which contains Drosophila STAM, has been sequenced. By comparison to cDNAs isolated and characterized, this region contains four tightly clustered genes: ial, mitochondrial porin, and the two newly discovered genes, STAM and DNZ1. Like its mouse and human homologs, STAM bears SH3 and ITAM domains. DNZ1 is a founding member of a sub-family of proteins bearing a DHHC/NEW1 zinc finger domain. Although these four genes are contained in a defined Deficiency overlap interval, no available P-element mutations in the region disrupt any of the genes, and no other discrete mutations in the genes have been identified. Among the four genes, ial and STAM share a common 5′ control region, suggesting coordinate expression. Developmental Northern data and embryonic and ovariole expression data show that STAM and ial expression are correlated. The other two genes in the cluster appear to be expressed at constitutive levels throughout development.

Introduction

A number of varied cytokine-receptor initiated signaling processes are mediated by Janus kinases (Jaks) in vertebrates. Many interleukins and related cytokines bind their appropriate specific receptors, and trigger them to intracellularly bind and activate their cognate Jak family member [for a review, see Taniguchi (1995)]. Heightened phosphorylation by the relevant receptor bound Jak cellular tyrosine kinase ensues both as autophosphorylation and as transphosphorylation on selected downstream effector proteins (Ihle et al., 1995). One of the best studied effectors of this class is the STAT (signal transducers and activators of transcription) family of proteins, whose phosphorylations by Jaks induce them to undergo translocation to the cell nucleus, where they act to modulate transcription (see Darnell et al., 1994). By means of these receptor-Jak-STAT signaling modules, ligand initiated processes that lead to cell-fate decisions on proliferation and differentiation are direct and rapid. However, many critical biological effects, such as STAT-independent myc induction by cytokines, are mediated by Jak signaling in which alternative second effectors have been postulated (Watanabe et al., 1996), such as STAM.

STAM (signal transducing adapter molecule) acts downstream of Jak, once induced by IL-2 or other cytokines, in human hematopoietic cells (Takeshita et al., 1996, Takeshita et al., 1997). STAM contains an SH3 domain and an ITAM (immunoreceptor tyrosine-based activation motif) domain (Takeshita et al., 1996). It associates with Jaks via its ITAM region, and is phosphorylated by Jaks in response to cytokine stimulation (Takeshita et al., 1997). Furthermore, close association has been established between STAM and the product of the Hrs (hepatocyte growth factor regulated tyrosine kinase substrate) gene, which is also phosphorylated in response to cytokine signaling (Asao et al., 1997). Together, STAM and Hrs seem to further Jak pathway signaling as an integrated complex (Asao et al., 1997).

In Drosophila melanogaster, the Jak kinase gene, hopscotch (hop), is required maternally and zygotically for early segmentation (Binari and Perrimon, 1994). Embryos without any contribution of hop lack specific body pattern elements. Those elements' absence identify hop as a gene acting in concert with gap genes, and upstream of pair-rule genes (see Hou and Perrimon, 1997). The gene is involved in additional post-segmentation developmental processes, where it is important for cell proliferation (Harrison et al., 1995). Both hop and the interacting STAT homolog STAT92E are essential for hemocyte differentiation and proliferation. A gain of function mutation, hopTum-l, and a STAT92E (marelle) mutation give rise to melanotic tumors due to overproliferation of hemocytes (Harrison et al., 1995, Hou et al., 1996, Yan et al., 1996). These bear some resemblance to leukemic overgrowth of cells in mammals. As an additional Jak-STAT pathway constituent, the mutation unpaired (upd) (Wieschaus et al., 1984) has been implicated by genetic and phenotypic means as a possible upstream ligand. No cognate receptor has yet been implicated.

In our survey of a 16-kb genomic region surrounding the serine–threonine kinase encoding ial (IplI-aurora like) gene (Reich et al., submitted), we have found a STAM homolog in Drosophila melanogaster. The discovery of STAM and Hrs homologs (Wides, unpublished) in flies extends the assertion that the Drosophila Jak pathway closely mirrors that of mammals and is likely to contain homologs of all key members of the mammalian pathway.

Drosophila STAM is immediately adjacent to the ial gene, is transcribed from the opposite DNA strand, and shares 5′ control elements with ial. By all measures of expression, STAM and ial are coordinately expressed. Two adjacent genes in the region, mitochondrial porin and the newly detected DNZ1, are in close quarters with the two genes, which affords an overview of a tightly packed multigene cluster.

Section snippets

Sequence of 20 kb of genomic sequence at 32B

From among the three overlapping genomic clones proven to contain ial (P1 clone DS00387, cosmid 35D1, and cosmid 198F4) (Cai et al., 1994, Hartl et al., 1994), cosmid clone 198F4 was chosen for extensive mapping and characterization. Restriction enzyme digestions were carried out in order to establish a large-scale restriction map of the genomic region (Reich et al., submitted). A 16-kb EcoRI fragment from the 198F4 insert was determined to include ial. This 16-kb fragment was subcloned into

The genes ial, STAM, DNZ1, and mitochondrial porin are clustered at 32B

In order to characterize the ial gene fully (Reich et al., submitted), we sequenced 16 kb of genomic DNA at this locus. A 16-kb EcoRI fragment of the cosmid clone 198F4 (Siden-Kiamos et al., 1990), was subcloned into bluescript, then randomly sheared and size-selected for 1500-bp fragments to optimize for sequencing. These fragments were randomly subcloned into an M13 vector for robotic-assisted ‘shotgun’ sequencing. The entire generated 16-kb sequence is assigned the GenBank Accession No.

The 32B region of chromosome 2L

The STAM, ial, DNZ1, and mitochondrial porin genes cluster in a 13-kb region of the genomic DNA at 32B in the Drosophila genome. Distal to this chromosomal region lie 7 kb of DNA with no discernible transcripts. We established the absence of transcripts in this 7 kb by the lack of bands on Northerns of RNA taken from varied developmental times, by the lack of cDNAs recovered from this region, and from a lack of EST sequences from any database corresponding to sequences in this region.

Except for

Acknowledgements

We would like to thank the following for materials kindly supplied: the European Drosophila genome project for Cosmid clones; the Berkeley Drosophila genome project (BDGP) for P1 clones; and A. Spradling, G. Rubin, T. Lavery, I. Kiss and BDGP for P-element disruption line flies. Many thanks to D. Lancet and E. Ben-Asher of the Genome Resource Laboratory at the Weizmann Institute of Science for collaborating on the large-scale sequencing approach, and to T. Mehlman and group for automated

References (39)

  • S. Watanabe et al.

    JAK2 is essential for activation of c-fos and c-myc promoter and cell proliferation through the human granulocyte-macrophage colony-stimulating factor receptor in BA/F3 cells

    J. Biol. Chem.

    (1996)
  • R. Binari et al.

    Stripe-specific regulation of pair-rule genes by hopscotch, a putative Jak family tyrosine kinase in Drosophila

    Genes Dev.

    (1994)
  • S. Bohm et al.

    Variations of the C2H2 zinc finger motif in the yeast genome and classification of yeast zinc finger proteins

    NAR

    (1997)
  • H. Cai et al.

    A yeast artificial chromosome map of the Drosophila genome

    Genetics

    (1994)
  • J.E.J. Darnell et al.

    Jak-STAT pathways and transcriptional activation in response to IFNs and other extracellular signaling proteins

    Science

    (1994)
  • D.A. Harrison et al.

    Activation of a Drosophila Janus kinase (JAK) causes hematopoietic neoplasia and developmental defects

    EMBO J.

    (1995)
  • D.L. Hartl et al.

    Genome structure and evolution in Drosophila: applications of the framework P1 map

    Proc. Natl. Acad. Sci. USA

    (1994)
  • J.N. Ihle et al.

    Signaling through the hematopoietic cytokine receptors

    Annu. Rev. Immunol.

    (1995)
  • K. Kongsuwan et al.

    A Drosophila Minute gene encodes a ribosomal protein

    Nature

    (1985)
  • Cited by (0)

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