Aphysical and functional link between the nuclear pore complex (NPC) and the spindle checkpoint machinery has been established in the yeast Saccharomyces cerevisiae. We show that two proteins required for the execution of the spindle checkpoint, Mad1p and Mad2p, reside predominantly at the NPC throughout the cell cycle. There they are associated with a subcomplex of nucleoporins containing Nup53p, Nup170p, and Nup157p. The association of the Mad1p–Mad2p complex with the NPC requires Mad1p and is mediated in part by Nup53p. On activation of the spindle checkpoint, we detect changes in the interactions between these proteins, including the release of Mad2p (but not Mad1p) from the NPC and the accumulation of Mad2p at kinetochores. Accompanying these events is the Nup53p-dependent hyperphosphorylation of Mad1p. On the basis of these results and genetic analysis of double mutants, we propose a model in which Mad1p bound to a Nup53p-containing complex sequesters Mad2p at the NPC until its release by activation of the spindle checkpoint. Furthermore, we show that the association of Mad1p with the NPC is not passive and that it plays a role in nuclear transport.

In addition to its role in nucleocytoplasmic transport, the nuclear pore complex (NPC) acts as a docking site for proteins whose apparent primary cellular functions are unrelated to nuclear transport, including Mad1p and Mad2p, two proteins of the spindle assembly checkpoint (SAC) machinery. To understand this relationship, we have mapped domains of yeast Saccharomyces cerevisiae Mad1p that interact with the nuclear transport machinery, including further defining its interactions with the NPC. We showed that a Kap95p/Kap60p-dependent nuclear localization signal, positioned in the C-terminal third of Mad1p, is required for its efficient targeting to the NPC. At the NPC, Mad1p interacts with Nup53p and a presumed Nup60p/Mlp1p/Mlp2p complex through two coiled coil regions within its N terminus. When the SAC is activated, a portion of Mad1p is recruited to kinetochores through an interaction that is mediated by the C-terminal region of Mad1p and requires energy. We showed using photobleaching analysis that in nocodazole-arrested cells Mad1p rapidly cycles between the Mlp proteins and kinetochores. Our further analysis also showed that only the C terminus of Mad1p is required for SAC function and that the NPC, through Nup53p, may act to regulate the duration of the SAC response. INTRODUCTIONA defining feature of eukaryotic cells is the physical separation of the nuclear content from the remainder of the cell by the nuclear envelope (NE) membrane. All transport across this double membrane is regulated by massive protein structures termed nuclear pore complexes (NPCs). These highly conserved transport channels are composed of repetitive subunits that together form eightfold symmetrical structures that occupy transcisternal pores across the NE (Suntharalingam and Wente, 2003). In both yeast and mammalian cells, the NPCs are composed of ϳ30 different proteins termed nucleoporins (nups) (Rout et al., 2000;Cronshaw et al., 2002), all of which are present in this structure in multiple copies. Macromolecular cargos destined to either enter or exit the nucleus contain specific sequences referred to as nuclear localization sequences (NLSs) or nuclear export sequences (NESs), respectively. These sequences are recognized by soluble cargo-binding proteins termed karyopherins (kaps) of which there are ϳ14 in yeast. Kap/cargo complexes then bind to the NPC through interactions between the kaps and a subset of nups that contain phenylalanine-glycine repeats. These nups line the translocation channel, and, through an as yet ill-defined mechanism, facilitate transport through the NPC. A key energy-contributing player in the nuclear transport machinery is the small GTPase Ran. Both the nuclear localization of RanGTP and its conversion to RanGDP play key roles in transport termination steps, the recycling of kaps, and the formation of nuclear export complexes.Recently, a growing body of evidence has accumulated implicating the NPC and NPC-associated components in additional functions outside of nuclear transport. For example, the Saccha...

Cover sheet Cover sheetTitle Re-evaluation of contact relationships between the Ordovician volcanic belts and the quartz-rich turbidites of the Lachlan Orogen

The modes of speciation that are thought to have contributed most to the generation of biodiversity require population di¡erentiation as the initial stage in the speciation process. Consequently, a complete understanding of the mechanisms of speciation requires that the process be examined not just after speciation is complete, or nearly so, but also much earlier. Because reproductive isolation de¢nes biological species, and it evolves slowly, study of the process may require a prohibitive span of time. Even if speciation could be observed directly, selection of populations in the process of speciation is typically di¤cult or impossible, because those that will ultimately undergo speciation cannot be distinguished from those that will di¡er-entiate but never assume the status of new biological species. One means of circumventing this problem is to study speciation in taxa comprising several sibling species, at least one of which exhibits extensive population di¡erentiation. We illustrate this approach by exploring patterns of population variation in the postglacial radiation of the threespine stickleback, Gasterosteus aculeatus. We focus on lacustrine populations and species within this complex, demonstrating parallel axes of divergence within populations, among populations and among species. The pattern that emerges is one of parallel relationships between phenotype and ¢tness at all three hierarchical levels, a pattern that facilitates exploration of the causes and consequences of speciation and secondary contact. A second outcome of this exploration is the observation that speciation can be the consequence of a cascade of e¡ects, beginning with selection on trophic or other characteristics that in turn force the evolution of other population characteristics that precipitate speciation. Neither of these conclusions could have been reached without comparative studies of wild populations at several hierarchical levels, a conclusion reinforced by a brief survey of similar e¡orts to elucidate the process of speciation. We address the issues most likely to be resolved using this approach, and suggest that comparisons of natural variation within taxa at several hierarchical levels may substantially increase our understanding of the speciation process.

Gold commonly occurs in pyrite (FeS2) as "invisible" or refractory gold, as is the case at the giant Lihir (i.e., Ladolam) hybrid alkali-type gold deposit in Papua New Guinea. The Lihir gold deposit is also unique as it the exemplar of a telescoped ore deposit, whereby volcanic sector collapse led to superimposition of shallow-level gold-rich epithermal mineralization upon preexisting, but genetically related, porphyry-style alteration. While this superimposition led to a giant 56 Moz gold resource, it also created complications with regards to ore processing, specifically with regards to the difficulties in mineral processing of the refractory gold-rich pyritic ore.We have analyzed trace element zonation and composition of pyrite grains, using LA-ICP-MS imaging coupled with NaOCl etching, from a subset of spatially and paragenetically constrained pyrite-bearing samples from the Lienetz orebody. Pyrite grains belong to either porphyry-or epithermal-stages, or are composite pyrite grains with a multi-stage history. Trace element zonation and metal contents are unique to pyrite from each paragenetic event, providing insights into the nature of the mineralizing fluids. Early generations of coarse-grained pyrites that formed under higher temperature porphyry-style conditions have low trace element contents compared to epithermal-stage pyrites, except for Co, Ni and Se. Later generations of oscillatory zoned pyrites that formed under lower temperature epithermal conditions are comparatively enriched in trace elements such as As, Mo, Ag, Sb, Au and Tl. The composite pyrites are relatively coarse-grained and display textural and geochemical evidence of modification (i.e., dissolution and re-precipitation). They are interpreted to be porphyry-stage pyrite grains that have been overgrown by rims of delicate banded epithermal-style pyrite enriched in gold, arsenic and other trace elements.The composite pyrite grains are volumetrically dominant in the deep-seated anhydrite zone at Lienetz. Because gold is concentrated only along the rims of these pyrite grains, they can be subjected to a shorter period of oxidation and leaching to liberate most of their gold. This is in contrast for areas dominated by high-grade epithermal-stage mineralization where pyrite grains are arsenic-and gold-rich throughout, and thus require longer oxidation and processing time.Understanding gold deportment in telescoped deposits is therefore essential for optimising mineral processing and can impact significantly on the economics of mining these complex, hybrid ore deposits.