Androcam, a Drosophila calmodulin-related protein, is expressed specifically in the testis and decorates loop kl-3 of the Y chromosome

Lu, Alan Qing; Beckingham, Kathy

doi:10.1016/s0925-4773(00)00262-8

Cited by 13 publications

(15 citation statements)

References 42 publications

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“…Neither of the Drosophila CaM antibodies used previously for immunolocalization studies in other tissues (32) revealed specific staining for CaM on the actin cone fronts (22). Furthermore, immunoprecipitation experiments presented here showed that while CaM could be found in a complex with myosin VI in ovarian extracts, such an interaction was not detectable in testis extracts.…”

Section: Discussioncontrasting

confidence: 74%

“…We co-labeled wild-type testes with antibodies specific for myosin VI and Acam. The Acam antibody used, RU158, has a ϳ100-fold higher specificity for Acam than CaM (22). We found that in individualizing spermatids, myosin VI and Acam showed perfect co-localization in a series of discrete, tight bands (Fig.…”

Section: Resultsmentioning

confidence: 81%

“…Although Acam has a wider range of localization sites in the testis, previous studies indicated that one of its sites of accumulation is also on the actin cone fronts (22). To begin to ask if Acam and myosin VI function together at this site, we examined whether they show precise colocalization at this position.…”

Section: Resultsmentioning

confidence: 99%

“…In previous immunolocalization experiments (22) we failed to detect any concentration of CaM at the actin cone fronts, but given that this could reflect epitope masking we attempted co-immunoprecipitation as a more definitive assay for an interaction. Both in the presence and absence of calcium, we could not co-immunoprecipitate CaM from the testis with myosin VI antibodies (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…However, one clue comes from the discovery that a testis-specific CaM-like protein, Androcam (Acam), also localizes to the fronts of the actin cones in individualizing spermatids (22). Acam is 68% identical in overall sequence to Drosophila CaM (with the C-terminal domain being closely similar) but Acam transcripts are only detectable in the testis (22)(23)(24). In vitro Acam has different calcium affinities than CaM: the affinities of the strong and weak calcium binding sites are ϳ0.04 M and 100 M, respectively, compared with 0.15 M and 15 M for CaM (25).…”

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confidence: 99%

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Androcam Is a Tissue-specific Light Chain for Myosin VI in the Drosophila Testis

Frank

Martin²,

Gruender

et al. 2006

Journal of Biological Chemistry

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Myosin VI, a ubiquitously expressed unconventional myosin, has roles in a broad array of biological processes. Unusual for this motor family, myosin VI moves toward the minus (pointed) end of actin filaments. Myosin VI has two light chain binding sites that can both bind calmodulin (CaM). However unconventional myosins could use tissue-specific light chains to modify their activity. In the Drosophila testis, myosin VI is important for maintenance of moving actin structures, called actin cones, which mediate spermatid individualization. A CaM-related protein, Androcam (Acam), is abundantly expressed in the testis and like myosin VI, accumulates on these cones. We have investigated the possibility that Acam is a testis-specific light chain of Drosophila myosin VI. We find that Acam and myosin VI precisely colocalize at the leading edge of the actin cones and that myosin VI is necessary for this Acam localization. Further, myosin VI and Acam co-immunoprecipitate from the testis and interact in yeast two-hybrid assays. Finally Acam binds with high affinity to peptide versions of both myosin VI light chain binding sites. In contrast, although Drosophila CaM also shows high affinity interactions with these peptides, we cannot detect a CaM/myosin VI interaction in the testis. We conclude that Acam and not CaM acts as a myosin VI light chain in the Drosophila testis and hypothesize that it may alter the regulation of myosin VI in this tissue.The myosins constitute a superfamily of 18 classes (1 conventional and 17 unconventional) (1), all of which share sequence similarity in the motor domain. It is thought that they also share the ability to translocate along actin filaments. Myosins play roles in numerous cellular activities, such as division, endocytosis, cell movement, and organelle trafficking. In addition to the conserved motor domain, all myosins contain one or more conserved IQ motifs (consensus sequence IQXXXRGXXXR, where X is any amino acid) that bind calmodulin (CaM), 4 a ubiquitous calcium sensor protein, or CaM-like light chains (2-4). The ATPase activity and motility of unconventional myosins can be regulated by calcium binding to CaM or a CaMlike protein (5).Members of the myosin VI class appear to be unique among the unconventional myosins in their direction of translocation along actin. They move toward the pointed, or minus, end of actin filaments (6) whereas all other myosins tested move toward the barbed, or plus, end. Recent structural studies of pig myosin VI (7) indicate that this reversed directionality is associated with one of the two unique inserts in myosin VI, termed insert 2. This sequence is located between the converter region of the motor domain and the IQ motif, and its converter-proximal sequences are proposed to redirect the lever arm in the opposite direction relative to other myosins.Insert 2 is also proposed to perform a second, structural, role in myosin VI. In the pig crystal structure, its more C-terminal sequences form a continuous helix with the IQ motif, thus potentially exte...

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Section: Discussioncontrasting

confidence: 74%

Section: Resultsmentioning

confidence: 81%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Androcam Is a Tissue-specific Light Chain for Myosin VI in the Drosophila Testis

Frank

Martin²,

Gruender

et al. 2006

Journal of Biological Chemistry

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Autosomal control of the Y-chromosome kl-3 loop of Drosophila melanogaster

et al. 2004

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The Y chromosome of Drosophila melanogaster carries a limited number of loci necessary for male fertility that possess a series of unconventional features that still hinder a definition of their biological role: they have extremely large sizes; accommodate huge amounts of repetitive DNA; and develop prominent, lampbrush-like loops that bind a number of non-Y-encoded proteins. To obtain insight into the functional role of the loop-forming fertility factors, we characterized four autosomal male-sterile mutations that identify two loci we named loop unfolding protein-1 (lup-1) and loop unfolding protein-2 (lup-2). Biochemical and ultrastructural analysis revealed that neither of them impairs the synthesis of the putative dynein subunit encoded by the ORF localized within the kl-3 fertility factor. However, the stability of four dynein heavy chains is simultaneously affected in each mutant, together with the regular assembly of the axonemal dynein arms that are either absent or strongly reduced. These results indicate that the synthesis of the kl-3-encoded dynein can be uncoupled from the formation of the corresponding loop and suggest that this structure does not simply represent the cytological counterpart of a huge transcription unit, but must be regarded as a complex organelle serving some additional function necessary for male fertility.

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Co-transcriptional architecture in a Y loop in Drosophila melanogaster

2011

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The Y loops of Drosophila spermatocytes are formed by the expression of huge individual transcription units on the Y chromosome and their large size provides a unique system for the investigation of the organisation of transcription in intact nuclei. By labelling ribonucleo-protein (RNP) components, the loop chromatin and nascent transcripts in Y loop C, we reveal a highly structured organisation of RNP domains associated with nascent transcripts. We distinguish two types of RNP domain, a proximal domain that runs alongside the chromatin of loop C and a distal RNP domain that wraps around the proximal domain and the loop chromatin. The proximal domain is marked by the Pasilla protein, and separate distal subdomains are marked by the S5 antigen and Boule. We discuss the implications of this highly structured co-transcriptional architecture for the organisation of the process of transcription.

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Androcam, a Drosophila calmodulin-related protein, is expressed specifically in the testis and decorates loop kl-3 of the Y chromosome

Cited by 13 publications

References 42 publications

Androcam Is a Tissue-specific Light Chain for Myosin VI in the Drosophila Testis

Androcam Is a Tissue-specific Light Chain for Myosin VI in the Drosophila Testis

Autosomal control of the Y-chromosome kl-3 loop of Drosophila melanogaster

Co-transcriptional architecture in a Y loop in Drosophila melanogaster

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