We have previously demonstrated [Rihs, H.‐P. and Peters, R. (1989) EMBO J., 8, 1479–1484] that the nuclear transport of recombinant proteins in which short fragments of the SV40 T‐antigen are fused to the amino terminus of Escherichia coli beta‐galactosidase is dependent on both the nuclear localization sequence (NLS, T‐antigen residues 126–132) and a phosphorylation‐site‐containing sequence (T‐antigen residues 111–125). While the NLS determines the specificity, the rate of transport is controlled by the phosphorylation‐site‐containing sequence. The present study furthers this observation and examines the role of the various phosphorylation sites. Purified, fluorescently labeled recombinant proteins were injected into the cytoplasm of Vero or hepatoma (HTC) cells and the kinetics of nuclear transport measured by laser microfluorimetry. By replacing serine and threonine residues known to be phosphorylated in vivo, we identified the casein kinase II (CK‐II) site S111/S112 to be the determining factor in the enhancement of the transport. Either of the residues 111 or 112 was sufficient to elicit the maximum transport enhancement. The other phosphorylation sites (S120, S123, T124) had no influence on the transport rate. Examination of the literature suggested that many proteins harboring a nuclear localization sequence also contain putative CK‐II sites at a distance of approximately 10–30 amino acid residues from the NLS. CK‐II has been previously implicated in the transmission of growth signals to the nucleus. Our results suggest that CK‐II may exert this role by controlling the rate of nuclear protein transport.

Nuclear import of conventional nuclear localization sequence (NLS)-containing proteins initially involves recognition by the importin (IMP)␣The entry of karyophilic proteins into the nucleus through the nuclear pore complex (NPC) 1 is effected by specific targeting signals called nuclear localization sequences (NLSs) (1, 2), and is a receptor-mediated (3, 4), energy-dependent (5, 6) process. The key factors involved are members of the NLS-recognizing importin/karyopherin family (7-11), the monomeric GTPase Ran/TC4 (12, 13), and auxiliary proteins such as NTF2/p10 (14, 15). In the first step, the NLS-containing protein is recognized by the importin (IMP) heterodimer through the NLS-binding IMP␣ subunit (3, 7, 9) and targeted to the NPC through the affinity of the IMP␤ subunit (8, 10, 11, 16) for NPC components (17, 18). In the second step requiring cytoplasmic RanGDP (19,20), the transport complex is translocated through the NPC (21), and IMP␣ and the NLS-bearing protein are released into the nucleoplasm through the action of Ran GTP (19). Alternative signal-mediated nuclear import pathways have recently been identified, where either IMP␤ itself (22-24) or related homologs (25-27) fulfill the role of both IMP␣ and -␤ in binding NLSs and targeting them to the NPC (25,26,28).Although NLS receptors from different species share structural and functional homology, experimental evidence suggests that nuclear import in plant cells has unique features compared with that in other eukaryotes. In contrast to the latter, in vitro transport in plant cells appears not to be inhibited by the nucleoporin-binding lectin wheat germ agglutinin and to occur at low temperature and in the absence of exogenously added cytosol (see Refs. 29 and 30). In addition, the NLS-binding IMP␣ subunit from Arabidopsis thaliana (At-IMP␣) shows nuclear envelope association (30,31) in similar fashion to IMP␤ in mammalian and other cell systems (8, 10, 11); IMP␣ in mammalian and yeast systems shows predominantly nucleoplasmic location as well as cell cycle-dependent localization in either cytoplasm or nucleus in Drosophila (32). A linkage of At-IMP␣ with the cytoskeleton has also recently been demonstrated, with a mechanistic role in nuclear import surmised (33). Because of these novel properties, we set out to quantitate the NLS binding properties of At-IMP␣ for the first time using an ELISA-based assay (34, 35). We find that At-IMP␣ binds NLSs of different types with high affinity independent of an IMP␤ subunit, in contrast to the IMP␣ subunits from mouse and yeast, which require their respective IMP␤ subunits to achieve high affinity binding (21, 34 -36). At-IMP␣, together with Ran/ TC4 and NTF2 and in the absence of IMP␤, was able to mediate nuclear import in vitro to levels comparable with those mediated by mouse IMP␣/␤ (m-IMP␣/␤). m-IMP␣ was unable to mediate nuclear import in the absence of m-IMP␤. At-IMP␣ thus shows unique properties, being able to fulfill both NLS recognition and nuclear import in the absence of IMP␤.

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IgE-mediated Cannabis (C. sativa, marihuana) allergy seems to be on the rise. Both active and passive exposure to cannabis allergens may trigger a C. sativa sensitization and/or allergy. The clinical presentation of a C. sativa allergy varies from mild to life-threatening reactions and often seems to depend on the route of exposure. In addition, sensitization to cannabis allergens can result in various cross-allergies, mostly for plant foods. This clinical entity, designated as the 'cannabis-fruit/vegetable syndrome', might also imply cross-reactivity with tobacco, natural latex and plant-food-derived alcoholic beverages. Hitherto, these crossallergies are predominantly reported in Europe and appear mainly to rely upon cross-reactivity between nonspecific lipid transfer proteins or thaumatin-like proteins present in C. sativa and their homologues, ubiquitously distributed throughout plant kingdom. At present, diagnosis of cannabis-related allergies predominantly rests upon a thorough history completed with skin testing using native extracts from crushed buds and leaves. However, quantification of specific IgE antibodies and basophil activation tests can also be helpful to establish correct diagnosis. In the absence of a cure, treatment comprises absolute avoidance measures. Whether avoidance of further use will halt the extension of related cross-allergies remains uncertain.Cannabis sativa (C. sativa) is an annual, dioecious and anemophilous flowering plant (order: Rosales, family Cannabaceae) that is native to central and southern Asia and the Caucasian region. Different preparations [dried flowering tops, hashish, hashish oil] are obtained from cannabis varieties containing elevated levels of cannabinoids, especially delta-9-tetrahydrocannabinol (THC), several of them being more or less potent psychoactive substances. Although, today, cannabis use is still illegal in most countries, it is widespread for its relaxing and euphoric effects. Furthermore, worldwide the illegal status of the drug has gained more and more resistance recently, resulting in legalization of both sale and possession of marijuana in Colorado, Alaska, Oregan and Washington, for example, both for medicinal and recreational use (1). Different European countries are debating the legalization of cannabis as well. While consumption of cannabis has been legal under certain conditions for a while

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