Identification of a coordinate regulator of interleukins 4, 13, and 5 by cross-species sequence comparisons

Long-range regulatory elements are difficult to discover experimentally; however, they tend to be conserved among mammals, suggesting that cross-species sequence comparisons should identify them. To search for regulatory sequences, we examined about 1 megabase of orthologous human and mouse sequences for conserved noncoding elements with greater than or equal to 70% identity over at least 100 base pairs. Ninety noncoding sequences meeting these criteria were discovered, and the analysis of 15 of these elements found that about 70% were conserved across mammals. Characterization of the largest element in yeast artificial chromosome transgenic mice revealed it to be a coordinate regulator of three genes, interleukin-4, interleukin-13, and interleukin-5, spread over 120 kilobases.

Disruption of axonal transport and neuronal viability by amyloid precursor protein mutations in Drosophila

We tested the hypothesis that amyloid precursor protein (APP) and its relatives function as vesicular receptor proteins for kinesin-I. Deletion of the Drosophila APP-like gene (Appl) or overexpression of human APP695 or APPL constructs caused axonal transport phenotypes similar to kinesin and dynein mutants. Genetic reduction of kinesin-I expression enhanced while genetic reduction of dynein expression suppressed these phenotypes. Deletion of the C terminus of APP695 or APPL, including the kinesin binding region, disrupted axonal transport of APP695 and APPL and abolished the organelle accumulation phenotype. Neuronal apoptosis was induced only by overexpression of constructs containing both the C-terminal and Abeta regions of APP695. We discuss the possibility that axonal transport disruption may play a role in the neurodegenerative pathology of Alzheimer's disease.

Kinesin family in murine central nervous system

In neuronal axons, various kinds of membranous components are transported along microtubules bidirectionally. However, only two kinds of mechanochemical motor proteins, kinesin and brain dynein, had been identified as transporters of membranous organelles in mammalian neurons. Recently, a series of genes that encode proteins closely related to kinesin heavy chain were identified in several organisms including Schizosaccharomyces pombe, Aspergillus niddulans, Saccharomyces cerevisiae, Caenorhabditus elegans, and Drosophila. Most of these members of the kinesin family are implicated in mechanisms of mitosis or meiosis. To address the mechanism of intracellular organelle transport at a molecular level, we have cloned and characterized five different members (KIF1-5), that encode the microtubule-associated motor domain homologous to kinesin heavy chain, in murine brain tissue. Homology analysis of amino acid sequence indicated that KIF1 and KIF5 are murine counterparts of unc104 and kinesin heavy chain, respectively, while KIF2, KIF3, and KIF4 are as yet unidentified new species. Complete amino acid sequence of KIF3 revealed that KIF3 consists of NH2-terminal motor domain, central alpha-helical rod domain, and COOH-terminal globular domain. Complete amino acid sequence of KIF2 revealed that KIF2 consists of NH2-terminal globular domain, central motor domain, and COOH-terminal alpha-helical rod domain. This is the first identification of the kinesin-related protein which has its motor domain at the central part in its primary structure. Northern blot analysis revealed that KIF1, KIF3, and KIF5 are expressed almost exclusively in murine brain, whereas KIF2 and KIF4 are expressed in brain as well as in other tissues. All these members of the kinesin family are expressed in the same type of neurons, and thus each one of them may transport its specific organelle in the murine central nervous system.

Essential role of a kinesin-like protein in Arabidopsis trichome morphogenesis

Little is known about how cell shape is controlled. We are using the morphogenesis of trichomes (plant hairs) on the plant Arabidopsis thaliana as a model to study how cell shape is controlled. Wild-type Arabidopsis trichomes are large, single epidermal cells with a stalk and three or four branches, whereas in zwichel (zwi) mutants the trichomes have a shortened stalk and only two branches. To further understand the role of the ZWI gene in trichome morphogenesis we have cloned the wild-type ZWICHEL (ZWI) gene by T-DNA tagging, and report here that it encodes a member of the kinesin superfamily of microtubule motor proteins. Kinesin proteins transport diverse cellular materials in a directional manner along microtubules. Kinesin-like proteins are characterized by a highly conserved "head" region that comprises the motor domain, and a nonconserved "tail" region that is thought to participate in recognition and binding of the appropriate cargo.

Suppression of kinesin expression in cultured hippocampal neurons using antisense oligonucleotides

Kinesin, a microtubule-based force-generating molecule, is thought to translocate organelles along microtubules. To examine the function of kinesin in neurons, we sought to suppress kinesin heavy chain (KHC) expression in cultured hippocampal neurons using antisense oligonucleotides and study the phenotype of these KHC "null" cells. Two different antisense oligonucleotides complementary to the KHC sequence reduced the protein levels of the heavy chain by greater than 95% within 24 h after application and produced identical phenotypes. After inhibition of KHC expression for 24 or 48 h, neurons extended an array of neurites often with one neurite longer than the others; however, the length of all these neurites was significantly reduced. Inhibition of KHC expression also altered the distribution of GAP-43 and synapsin I, two proteins thought to be transported in association with membranous organelles. These proteins, which are normally localized at the tips of growing neurites, were confined to the cell body in antisense-treated cells. Treatment of the cells with the corresponding sense oligonucleotides affected neither the distribution of GAP-43 and synapsin I, nor the length of neurites. A full recovery of neurite length occurred after removal of the antisense oligonucleotides from the medium. These data indicate that KHC plays a role in the anterograde translocation of vesicles containing GAP-43 and synapsin I. A deficiency in vesicle delivery may also explain the inhibition of neurite outgrowth. Despite the inhibition of KHC and the failure of GAP-43 and synapsin I to move out of the cell body, hippocampal neurons can extend processes and acquire as asymmetric morphology.

Reciprocal localization of Nod and kinesin fusion proteins indicates microtubule polarity in the Drosophila oocyte, epithelium, neuron and muscle

Polarization of the microtubule cytoskeleton is an early event in establishment of anterior-posterior polarity for the Drosophila oocyte. During stages 8–9 of oogenesis, when oskar mRNA is transported to the posterior pole of the oocyte, a fusion protein consisting of the plus-end-directed microtubule motor kinesin and beta-galactosidase (Kin:beta gal) similarly localizes to the posterior pole, thereby suggesting that plus ends of microtubules are pointed to the posterior. In this paper, we have substituted the motor domain of Kin:beta gal with the putative motor domain (head) from the kinesin-related protein Nod. In cells with defined microtubule polarity, the Nod:beta gal fusion protein is an in vivo minus-end reporter for microtubules. Nod:beta gal localizes to apical cytoplasm in epithelial cells and to the poles of mitotic spindles in dividing cells. In stage 8–10 oocytes, the Nod fusion localizes to the anterior margin, thus supporting the hypothesis that minus ends of microtubules at these stages are primarily at the anterior margin of the oocyte. The fusion protein also suggests a polarity to the microtubule cytoskeleton of dendrites and muscle fibers, as it accumulates at the ends of dendrites in the embryonic PNS and is excluded from terminal cytoplasm in embryonic muscle. Finally, the reciprocal in vivo localization of Nod:beta gal and Kin:beta gal suggests that the head of Nod may be a minus-end-directed motor.

Kinesin superfamily protein 3 (KIF3) motor transports fodrin-associating vesicles important for neurite building

Kinesin superfamily proteins (KIFs) comprise several dozen molecular motor proteins. The KIF3 heterotrimer complex is one of the most abundantly and ubiquitously expressed KIFs in mammalian cells. To unveil the functions of KIF3, microinjection of function-blocking monovalent antibodies against KIF3 into cultured superior cervical ganglion (SCG) neurons was carried out. They significantly blocked fast axonal transport and brought about inhibition of neurite extension. A yeast two-hybrid binding assay revealed the association of fodrin with the KIF3 motor through KAP3. This was further confirmed by using vesicles collected from large bundles of axons (cauda equina), from which membranous vesicles could be prepared in pure preparations. Both immunoprecipitation and immunoelectron microscopy indicated the colocalization of fodrin and KIF3 on the same vesicles, the results reinforcing the evidence that the cargo of the KIF3 motor consists of fodrin-associating vesicles. In addition, pulse-labeling study implied partial comigration of both molecules as fast flow components. Taken together, the KIF3 motor is engaged in fast axonal transport that conveys membranous components important for neurite extension.

Overexpression of motor protein KIF17 enhances spatial and working memory in transgenic mice

The kinesin superfamily proteins (KIFs) play essential roles in receptor transportation along the microtubules. KIF17 transports the N-methyl-d-aspartate receptor NR2B subunit in vitro, but its role in vivo is unknown. To clarify this role, we generated transgenic mice overexpressing KIF17 tagged with GFP. The KIF17 transgenic mice exhibited enhanced learning and memory in a series of behavioral tasks, up-regulated NR2B expression with the potential involvement of a transcriptional factor, the cAMP-dependent response element-binding protein, and increased phosphorylation of the cAMP-dependent response element-binding protein. Our results suggest that the motor protein KIF17 contributes to neuronal events required for learning and memory by trafficking fundamental N-methyl-d-aspartate-type glutamate receptors.

Kinesin family deregulation coordinated by bromodomain protein ANCCA and histone methyltransferase MLL for breast cancer cell growth, survival, and tamoxifen resistance

Kinesins are a superfamily of motor proteins and often deregulated in different cancers. However, the mechanism of their deregulation has been poorly understood. Through examining kinesin gene family expression in estrogen receptor (ER)-positive breast cancer cells, we found that estrogen stimulation of cancer cell proliferation involves a concerted regulation of specific kinesins. Estrogen strongly induces expression of 19 kinesin genes such as Kif4A/4B, Kif5A/5B, Kif10, Kif11, Kif15, Kif18A/18B, Kif20A/20B, Kif21, Kif23, Kif24, Kif25, and KifC1, whereas suppresses the expression of seven others, including Kif1A, Kif1C, Kif7, and KifC3. Interestingly, the bromodomain protein ANCCA/ATAD2, previously shown to be an estrogen-induced chromatin regulator, plays a crucial role in the up- and downregulation of kinesins by estrogen. Its overexpression drives estrogen-independent upregulation of specific kinesins. Mechanistically, ANCCA (AAA nuclear coregulator cancer associated) mediates E2-dependent recruitment of E2F and MLL1 histone methyltransferase at kinesin gene promoters for gene activation-associated H3K4me3 methylation. Importantly, elevated levels of Kif4A, Kif15, Kif20A, and Kif23 correlate with that of ANCCA in the tumors and with poor relapse-free survival of patients with ER-positive breast cancer. Their knockdown strongly impeded proliferation and induced apoptosis of both tamoxifen-sensitive and resistant cancer cells. Together, the study reveals ANCCA as a key mediator of kinesin family deregulation in breast cancer and the crucial role of multiple kinesins in growth and survival of the tumor cells.

IMPLICATIONS

These findings support the development of novel inhibitors of cancer-associated kinesins and their regulator ANCCA for effective treatment of cancers including tamoxifen-resistant breast cancers.

KIF2 is a new microtubule-based anterograde motor that transports membranous organelles distinct from those carried by kinesin heavy chain or KIF3A/B

Kinesin is known as a representative cytoskeletal motor protein that is engaged in cell division and axonal transport. In addition to the mutant assay, recent advances using the PCR cloning technique have elucidated the existence of many kinds of kinesin-related proteins in yeast, Drosophila, and mice. We previously cloned five different members of kinesin superfamily proteins (KIFs) in mouse brain (Aizawa, H., Y. Sekine, R. Takemura, Z. Zhang, M. Nangaku, and N. Hirokawa. 1992. J. Cell Biol. 119:1287-1296) and demonstrated that one of them, KIF3A, is an anterograde motor (Kondo, S., R. Sato-Yashitake, Y. Noda, H. Aizawa, T. Nakata, Y. Matsuura, and N. Hirokawa. J. Cell Biol. 1994. 125:1095-1107). We have now characterized another axonal transport motor, KIF2. Different from other KIFs, KIF2 is a central type motor, since its motor domain is located in the center of the molecule. Recombinant KIF2 exists as a dimer with a bigger head and plus-end directionally moves microtubules at a velocity of 0.47 +/- 0.11 microns/s, which is two thirds that of kinesin's. Immunocytological examination showed that native KIF2 is abundant in developing axons and that it accumulates in the proximal region of the ligated nerves after a 20-h ligation. Soluble KIF2 exists without a light chain, and KIF2's associated-vesicles, immunoprecipitated by anti-KIF2 antibody, are different from those carried by existing motors such as kinesin and KIF3A. They are also distinct from synaptic vesicles, although KIF2 is accumulated in so-called synaptic vesicle fractions and embryonal growth cone particles. Our results strongly suggest that KIF2 functions as a new anterograde motor, being specialized for a particular group of membranous organelles involved in fast axonal transport.

Two-dimensional tracking of ncd motility by back focal plane interferometry

A technique for detecting the displacement of micron-sized optically trapped probes using far-field interference is introduced, theoretically explained, and used to study the motility of the ncd motor protein. Bead motions in the focal plane relative to the optical trap were detected by measuring laser intensity shifts in the back-focal plane of the microscope condenser by projection on a quadrant diode. This detection method is two-dimensional, largely independent of the position of the trap in the field of view and has approximately 10-micros time resolution. The high resolution makes it possible to apply spectral analysis to measure dynamic parameters such as local viscosity and attachment compliance. A simple quantitative theory for back-focal-plane detection was derived that shows that the laser intensity shifts are caused primarily by a far-field interference effect. The theory predicts the detector response to bead displacement, without adjustable parameters, with good accuracy. To demonstrate the potential of the method, the ATP-dependent motility of ncd, a kinesin-related motor protein, was observed with an in vitro bead assay. A fusion protein consisting of truncated ncd (amino acids 195-685) fused with glutathione-S-transferase was adsorbed to silica beads, and the axial and lateral motions of the beads along the microtubule surface were observed with high spatial and temporal resolution. The average axial velocity of the ncd-coated beads was 230 +/- 30 nm/s (average +/- SD). Spectral analysis of bead motion showed the increase in viscous drag near the surface; we also found that any elastic constraints of the moving motors are much smaller than the constraints due to binding in the presence of the nonhydrolyzable nucleotide adenylylimidodiphosphate.

Cloning and localization of a conventional kinesin motor expressed exclusively in neurons

Kinesin is a microtubule-based motor protein involved in organelle transport in neuronal and nonneuronal cells. Although a single kinesin motor has been thought to serve all cell types, we document here that neurons express a second conventional kinesin heavy chain (nKHC) that is 65% identical in amino acid sequence to the ubiquitously expressed kinesin heavy chain (uKHC). By preparing antibodies which distinguish between the two KHCs, we demonstrate that nKHC is a nucleotide-dependent microtubule-binding protein which partially cofractionates with membrane organelles. Immunolocalization experiments show that nKHC is distributed throughout the CNS but is highly enriched in subsets of neurons. In hippocampal neurons in culture, uKHC is distributed uniformly throughout the neuron, whereas nKHC is selectively concentrated in the cell body. These results demonstrate that mammalian neuronal tissue contains two conventional kinesin motors which may serve distinct functions in microtubule-based transport.

An internal motor kinesin is associated with the Golgi apparatus and plays a role in trichome morphogenesis in Arabidopsis

Members of the kinesin superfamily are microtubule-based motor proteins that transport molecules/organelles along microtubules. We have identified similar internal motor kinesins, Kinesin-13A, from the cotton Gossypium hirsutum and Arabidopsis thaliana. Their motor domains share high degree of similarity with those of internal motor kinesins of animals and protists in the MCAK/Kinesin13 subfamily. However, no significant sequence similarities were detected in sequences outside the motor domain. In Arabidopsis plants carrying the T-DNA knockout kinesin-13a-1 and kinesin-13a-2 mutations at the Kinesin-13A locus, >70% leaf trichomes had four branches, whereas wild-type trichomes had three. Immunofluorescent results showed that AtKinesin-13A and GhKinesin-13A localized to entire Golgi stacks. In both wild-type and kinesin-13a mutant cells, the Golgi stacks were frequently associated with microtubules and with actin microfilaments. Aggregation/clustering of Golgi stacks was often observed in the kinesin-13a mutant trichomes and other epidermal cells. This suggested that the distribution of the Golgi apparatus in cell cortex might require microtubules and Kinesin-13A, and the organization of Golgi stacks could play a regulatory role in trichome morphogenesis. Our results also indicate that plant kinesins in the MCAK/Kinesin-13 subfamily have evolved to take on different tasks than their animal counterparts.

Sequence and submolecular localization of the 115-kD accessory subunit of the heterotrimeric kinesin-II (KRP85/95) complex

The heterotrimeric kinesin-II holoenzyme purified from sea urchin (Strongylocentrotus purpuratus) eggs is assembled from two heterodimerized kinesin-related motor subunits of known sequence, together with a third, previously uncharacterized 115-kD subunit, SpKAP115. Using monospecific anti-SpKAP115 antibodies we have accomplished the molecular cloning and sequencing of the SpKAP115 subunit. The deduced sequence predicts a globular 95-kD non-motor "accessory" polypeptide rich in alpha-helical segments that are generally not predicted to form coiled coils. Electron microscopy of individual rotary shadowed kinesin-II holoenzymes also suggests that SpKAP115 is globular, with a somewhat asymmetric morphology. Moreover, the SpKAP115 subunit lies at one end of the 51-nm-long kinesin-II complex, being separated from the two presumptive motor domains by a approximately 26-nm-long rod, in a manner similar to the light chains (KLCs) of kinesin itself. This indicates that SpKAP115 and the KLCs may have analogous functions, yet SpKAP115 does not display significant sequence similarity with the KLCs. The results show that kinesin and kinesin-II are assembled from highly divergent accessory polypeptides together with kinesin related motor subunits (KRPs) containing conserved motor domains linked to divergent tails. Despite the lack of sequence conservation outside the motor domains, there is striking conservation of the ultrastructure of the kinesin and kinesin-II holoenzymes.

A plant-specific kinesin binds to actin microfilaments and interacts with cortical microtubules in cotton fibers

A novel kinesin, GhKCH1, has been identified from cotton (Gossypium hirsutum) fibers. GhKCH1 has a centrally located kinesin catalytic core, a signature neck peptide of minus end-directed kinesins, and a unique calponin homology (CH) domain at its N terminus. GhKCH1 and other CH domain-containing kinesins (KCHs) belong to a distinct branch of the minus end-directed kinesin subfamily. To date the KCH kinesins have been found only in higher plants. Because the CH domain is often found in actin-binding proteins, we proposed that GhKCH1 might play a role in mediating dynamic interaction between microtubules and actin microfilaments in cotton fibers. In an in vitro actin-binding assay, GhKCH1's N-terminal region including the CH domain interacted directly with actin microfilaments. In cotton fibers, GhKCH1 decorated cortical microtubules in a punctate manner. Occasionally GhKCH1 was found to be associated with transverse-cortical actin microfilaments, but never with axial actin cables in cotton fibers. Localization of GhKCH1 on cortical microtubules was independent of the integrity of actin microfilaments. Thus, GhKCH1 may play a role in organizing the actin network in coordination with the cortical microtubule array. These data also suggest that flowering plants may employ unique KCHs to coordinate actin microfilaments and microtubules during cell growth.

Exclusive expression of C. elegans osm-3 kinesin gene in chemosensory neurons open to the external environment

In Caenorhabditis elegans three genetic loci osm-3, unc-104 and unc-116 have been identified, which encode anterograde motor kinesin. Here we show that osm-3 encodes a 672 amino acid long kinesin-like protein (KLP) that contains all three functional domains similar to the kinesin heavy chain, including a globular motor region, an alpha-helical coiled-coil rod, and a globular tail region. OSM-3 shows homology in both the motor and rod domains with kinesins from divergent species such as mouse KIF3, and sea urchin KRP95, and also with the rod domains of several non-kinesin proteins, such as myosin, ezrin, outer membrane proteins alpha precursor OMPA, yeast intracellular protein transport USO1, and the rat neurofilament NF-H. Temporal and spatial expression of the osm-3::lacZ fusion gene during development is limited to an exclusive set of 26 chemosensory neurons whose dendritic endings are exposed to the external environment, including six IL2 neurons of the inner labial sensilla, eight pairs of amphid neurons (ADF, ADL, ASE, ASG, ASH, ASI, ASJ, ASK) in the head, and two pairs of phasmid neurons (PHA and PHB) in the tail. Our data are consistent with the known structural defects in the amphid and phasmid sensilla in osm-3 mutants and also show the expression of the gene in IL2 neurons. Temporally, the gene is differentially expressed in all three types of chemosensory sensilla. Further work on osm-3, unc-104 and unc-116 mutants should give insight into the in vivo functions of the kinesin family during C. elegans neurogenesis.

The FLA3 KAP subunit is required for localization of kinesin-2 to the site of flagellar assembly and processive anterograde intraflagellar transport

Intraflagellar transport (IFT) is a bidirectional process required for assembly and maintenance of cilia and flagella. Kinesin-2 is the anterograde IFT motor, and Dhc1b/Dhc2 drives retrograde IFT. To understand how either motor interacts with the IFT particle or how their activities might be coordinated, we characterized a ts mutation in the Chlamydomonas gene encoding KAP, the nonmotor subunit of Kinesin-2. The fla3-1 mutation is an amino acid substitution in a conserved C-terminal domain. fla3-1 strains assemble flagella at 21 degrees C, but cannot maintain them at 33 degrees C. Although the Kinesin-2 complex is present at both 21 and 33 degrees C, the fla3-1 Kinesin-2 complex is not efficiently targeted to or retained in the basal body region or flagella. Video-enhanced DIC microscopy of fla3-1 cells shows that the frequency of anterograde IFT particles is significantly reduced. Anterograde particles move at near wild-type velocities, but appear larger and pause more frequently in fla3-1. Transformation with an epitope-tagged KAP gene rescues all of the fla3-1 defects and results in preferential incorporation of tagged KAP complexes into flagella. KAP is therefore required for the localization of Kinesin-2 at the site of flagellar assembly and the efficient transport of anterograde IFT particles within flagella.

C. elegans osm-3 gene mediating osmotic avoidance behaviour encodes a kinesin-like protein

In the nematode Caenorhabditis elegans, mutants in osm-3 gene are known to be defective in osmotic avoidance, chemotaxis and dauer formation behaviours. To study the molecular basis of these pleiotropic defects we have cloned the osm-3 gene by germline transformation of osm-3 (p802) mutants through microinjection of the wild type genomic DNA. Northern analysis reveals a 3.0 kb transcript corresponding to osm-3. DNA sequencing of the transforming 4.3 kb fragment revealed a kinesin heavy chain-like protein, which contains conserved ATPase and microtubule binding domains. Our results are consistent with the previous EM data on osm-3 (p802) mutants that show an accumulation of dense matrix material in the amphid sheath cytoplasm and a shortened distal segment of the amphid channel cilium. These data suggest a kinesin-like role of the osm-3 product in axonal transport.

The Neurospora organelle motor: a distant relative of conventional kinesin with unconventional properties

The "conventional" kinesins comprise a conserved family of molecular motors for organelle transport that have been identified in various animal species. Organelle motors from other phyla have not yet been analyzed at the molecular level. Here we report the identification, biochemical and immunological characterization, and molecular cloning of a cytoplasmic motor in a "lower" eukaryote, the Ascomycete fungus Neurospora crassa. This motor, termed Nkin (for Neurospora kinesin), exhibits several unique structural and functional features, including a high rate of microtubule transport, a lack of copurifying light chains, a second P-loop motif, and an overall sequence organization reminiscent of a kinesin-like protein. However, a greater than average sequence homology in the motor domain and the presence of a highly conserved region in the C-terminus identify Nkin as a distant relative of the family of conventional kinesins. A molecular phylogenetic analysis suggests Nkin to have diverged early in the evolution of this family of motors. The discovery of Nkin may help identify domains important for specific biological functions in conventional kinesins.

Expression analysis of 6p22 genomic gain in retinoblastoma

To identify gene(s) targeted by 6p22 genomic gain, present in more than 50% retinoblastoma tumors, we used real-time RT-PCR to quantify the expression of seven genes in normal human retina and retinoblastoma. Six genes are located in the quantitative multiplex PCR-defined 0.6 Mb minimal region of gain at 6p22 (DEK, AOF1, TPMT, NHLRC1, KIF13A, and NUP153), and E2F3 is 2 Mb away from the minimal region of gain on 6p22. E2F3, DEK, KIF13A, and NUP153 were most frequently overexpressed in retinoblastoma with 6p genomic gain, compared with the normal adult human retina. E2F3 and DEK mRNA levels were increased in all human tumors showing 6p22 gain, as well as in mouse retinoblastoma induced by SV40 large T antigen expression in developing retina, compared with the normal controls (adult human retina and 7-day-old mouse retina, respectively). Only DEK showed statistically significant correlation of expression and genomic copy number (P = 0.019). E2F3 and DEK, but not NUP153, showed developmental regulation. E2F3 and DEK mRNA overexpression was always associated with protein overexpression, determined by immunoblotting or immunofluorescent staining of primary tumors, relative to the adjacent normal retina. E2F3 was strongly expressed in actively proliferating cells, while DEK was overexpressed in all tumor cells. Taking into account the proliferation-promoting role of E2F3, implication of E2F3 in bladder and prostate cancer, and the translocation and overexpression of DEK in leukemia, we conclude that either DEK or E2F3 (or both) are targeted by the 6p22 gain in retinoblastoma.

Armadillo repeat-containing kinesins and a NIMA-related kinase are required for epidermal-cell morphogenesis in Arabidopsis

The involvement of kinesin motor proteins in both cell-tip growth and cell-shape determination has been well characterized in various organisms. However, the functions of kinesins during cell morphogenesis in higher plants remain largely unknown. In the current study, we demonstrate that an armadillo repeat-containing kinesin-related protein, ARMADILLO REPEAT KINESIN1 (ARK1), is involved in root-hair morphogenesis. Microtubule polymers are more abundant in ark1 null allele root hairs, but analysis shows that these extra microtubules are concentrated in the endoplasm, and not in the cortical array, suggesting that ARK1 regulates tip growth by limiting the assembly and distribution of endoplasmic microtubules. The ARK1 gene has two homologues in the Arabidopsis genome, ARK2 and ARK3, and our results show that ARK2 is involved in root-cell morphogenesis. We further reveal that a NIMA-related protein kinase, NEK6, binds to the ARK family proteins and has pleiotropic effects on epidermal-cell morphogenesis, suggesting that NEK6 is involved in cell morphogenesis in Arabidopsis via microtubule functions associated with these armadillo repeat-containing kinesins. We discuss the function of NIMA-related protein kinases and armadillo repeat-containing kinesins in the cell morphogenesis of eukaryotes.

Kinesin participates in melanosomal movement along melanocyte dendrites

Movement of melanosomes along melanocyte dendrites is necessary for the transfer of melanin pigment from melanocytes to basal and suprabasal keratinocytes, an event critical to epidermal photoprotection and maintenance of normal skin color. Recent murine data suggest that in melanocyte dendrites the microtubule-associated melanosome movement is bidirectional and that actin-associated myosin V secures the peripheral melanosomes, preparing them to be transferred to surrounding keratinocytes. We now report that human melanocytes express high levels of kinesin, a molecule that participates in microtubule-associated transport of organelles in other cell types, and that ultrastructurally kinesin molecules are closely associated with melanosomes. To determine whether kinesin participates in melanosomal transport, cultured melanocytes were treated with sense or antisense oligonucleotides complementary to kinesin heavy chain sequences. Antisense oligonucleotides decreased kinesin protein levels and inhibited the bidirectional movement of the melanosomes, promoting their backward movement. Furthermore, guinea pigs were exposed to ultraviolet B irradiation, known to enhance transport of melanosomes from melanocytes to epidermal keratinocytes, and then were treated with kinesin sense or antisense oligonucleotides. The areas that were treated with kinesin antisense oligonucleotides showed significantly less pigmentation clinically and histologically than control (sense) oligonucleotide-treated areas. As observed ultrastructurally, in antisense-treated areas melanosomes remained in melanocyte dendrites but over several days were not transferred to the surrounding keratinocytes. Our study supports a major role for kinesin in microtubule-associated anterograde melanosomal transport in human melanocyte dendrites.

eagle, a member of the steroid receptor gene superfamily, is expressed in a subset of neuroblasts and regulates the fate of their putative progeny in the Drosophila CNS

We isolated and characterized the eagle gene, encoding a member of the steroid receptor superfamily in Drosophila. In the central nervous system eagle RNA was expressed in a limited number of cells. During stages 10 and 11, eagle RNA expression was observed in four neuroblasts, NB2-4, NB3-3, NB6-4 and NB7-3. Except for NB6-4, eagle RNA expression reached a maximum at the very beginning of expression or in the period of neuroblast delamination. Weak eagle RNA expression was also observed in a few putative progeny of NB7-3 during stages, late 11 and 12. All eagle RNA in abdominal segments disappeared at stage 13. Using an eagle-kinesin-lacZ fusion gene as a reporter, the division, migration, and axonogenesis in eagle-positive cells and their derivatives were examined. At stage 14, several types of neural or glial cells were detected which include EG and EW interneurons joining to the anterior and posterior commissures, respectively. Lack of eagle expression caused altered axonogenesis in an appreciable fraction of eagle-Kinesin-LacZ-positive neurons. Some EG cells failed to acquire the neural fate or underwent an extremely delayed differentiation, while EW neurons produced neurites in abnormal directions, suggesting that eagle may play a critical role in development of the progeny of eagle-positive neuroblasts.

The anatomy of flagellar microtubules: polarity, seam, junctions, and lattice

Although the overall structures of flagellar and cytoplasmic microtubules are understood, many details have remained a matter of debate. In particular, studies of the arrangement of tubulin subunits have been hampered by the low contrast of the tubulin subunits. This problem can now be addressed by the kinesin decoration technique. We have shown previously that the recombinant kinesin head domain binds to beta-tubulin, thus enhancing the contrast between alpha- and beta-tubulin in the electron microscope; this allows one to study the arrangement of tubulin dimers. Here we describe the lattices of the four different types of microtubules in eukaryotic flagellar axonemes (outer doublet A and B, central pair C1 and C2). They could all be labeled with kinesin head with an 8-nm axial periodicity (the tubulin dimer repeat), and all of them showed the B-surface lattice. This lattice is characterized by a 0.92-nm stagger between adjacent protofilaments. The B-lattice was observed on the axonemal microtubules as well as on extensions made by polymerizing porcine brain tubulin onto axonemal microtubules in the proximal and distal directions. This emphasizes that axonemal microtubules serve as high fidelity templates for seeding microtubules. The presence of a B-lattice implies that there must be a helical discontinuity ("seam") in the wall. This discontinuity is now placed near protofilaments A1 and A2 of the A-tubule, close to the inner junction between A- and B-microtubules. The two junctions differ in structure: the protofilaments of the inner junction (A1-B10) are staggered roughly by half a dimer, those of the outer junction (A10-B1) are roughly in register. Of the two junctions the inner one appears to have the stronger bonds, whereas the outer one is more labile and opens up easily, generating "composite sheets" with chevron patterns from which the polarity can be deduced (arrow in the plus direction). Decorated microtubules have a clear polarity. We find that all flagellar microtubules have the same polarities. The orientation of the dimers is such that the plus end terminates with a crown of alpha subunits, the minus end terminates with beta subunits which thus could be in contact with gamma-tubulin at the nucleation centers.

Cloning by insertional mutagenesis of a cDNA encoding Caenorhabditis elegans kinesin heavy chain

An additional genetic locus in Caenorhabditis elegans, unc-116, was identified in a screen for mutations resulting in defective locomotion. unc-116 was cloned by use of a transposon insertion mutant and the physical and genetic map of the genome. The cDNA sequence predicts an 815-amino acid protein. Based upon sequence comparison and secondary structure predictions, unc-116 encodes all three domains of the kinesin heavy chain: the motor, stalk, and tail. While the motor and tail domains have a high degree of identity to the equivalent domains of cloned kinesin heavy chains, the rodII domain of the stalk is significantly shorter than those previously reported and is not predicted to form a coiled-coil alpha-helix. Analysis of mutational defects in two C. elegans genes encoding anterograde motor molecules, unc-116 and unc-104, should provide insight into the in vivo functions of these members of the kinesin heavy chain superfamily.