No abstract

Abstract. The transport of Balbiani ring (BR) premessenger RNP particles in the larval salivary gland cells of the dipteran Chironomus tentans can be followed using electron microscopy. A BR RNP particle consists of an RNP ribbon bent into a ringlike structure. Upon translocation through the nuclear pore complex (NPC), the ribbon is straightened and enters the central channel of the NPC with the 5' end of the transcript in the lead. The translocating ribbon is likely to interact with the central channel but, in addition, the remaining portion of the ribbon ring makes contact with the periphery of the NPC. To determine the nature of this latter interaction, we have now studied the connections between the RNP particle and the border of the NPC during different stages of translocation using electron microscope tomography. It was observed that the 3' terminal domain of the ribbon always touches the nuclear ring of the NPC, but the precise area of contact is variable. Sometimes also a region on the opposite side of the ribbon ring reaches the nuclear ring. The pattern of contacts could be correlated to the stage of translocation, and it was concluded that the particle-nuclear ring interactions reflect a rotation of the ribbon ring in front of the central channel, the rotation being secondary to the successive translocation of the ribbon through the channel. The particle's mode of interaction with the NPC suggests that the initial contact between the 5' end domain of the ribbon and the entrance to the central channel is probably crucial to accomplish the ordered translocation of the premessenger RNP particle through the NPC.T n~ active transport of macromolecules between the nucleus and the cytoplasm occurs through the nuclear pore complex (NPC) 1 (for recent reviews about nucleo-cytoplasmic transport, see Gerace, 1992;Newmeyer, 1993;Dingwall and Laskey, 1992;Pant6 and Aebi, 1993). The NPC is tripartite and contains a central spoke-plug assembly surrounded by two coaxial rings, the nuclear ring facing the nucleus and the cytoplasmic ring the cytoplasm (Franke and Scheer, 1974;Maul, 1977;Hinshaw et al., 1992;Akey and Radermacher, 1993). The basic framework of the NPC is symmetric with an eightfold symmetry seen in the direction of transport (face-on direction) and a twofold symmetry between the two halves facing the nucleus and cytoplasm (edge-on direction). There are also peripheral structures making the NPC as a whole asymmetric (for discussion, see Pant6 and Aebi, 1993;Stewart, 1992). Notably, on both sides there are fibers connected to the rings and extending out into the surrounding medium for puta-

No abstract

Multiple endocrine neoplasia type 1 (MEN1) is tightly linked to the muscle-type glycogen phosphorylase (PYGM) gene in 11q13. This region of the human genome contains additional disease-related loci implicated in the development of insulin-dependent diabetes mellitus, familial paraganglioma type 2, spinocerebellar ataxia type 5, Bardet-Biedl syndrome and translocation t(11;17) described in B-cell non-Hodgkin's lymphoma. We approached cloning of candidate disease genes from 11q13 by large-scale genomic sequencing. We obtained > 106 kb of sequence around the PYGM gene and established a transcriptional map that includes: (i) two genes previously localized to 11q13, PYGM and a zinc-finger protein (ZFM1) gene; (ii) the germinal center kinase (GCK, human B-lymphocyte serine/threonine protein kinase) gene; (iii) a novel human CDC25-like (HCDC25L) gene; (iv) a dystrophia myotonica protein kinase-like (DMPKL) gene; and (v) a novel ubiquitously expressed gene of unknown function (germinal center kinase- neighboring gene, GCKNG).

No abstract