CELL SCIENCE AT A GLANCE 3791 Inner nuclear membrane farnesyl modification, which mediates transmembrane domain. Whereas LAP1 tight association with the INM. A-type isoforms bind preferentially to A-type proteins and the nuclear lamins are expressed only in lamins (A-type-lamin interactions are lamina differentiated cells. They are indicated in red; La A), and LAP2β to B- components of the peripheral lamina and type lamins, emerin associates with both Roland Foisner of structures in the nuclear interior. The lamin types. LAP2α is the most distantly Department of Biochemistry and Molecular Cell lamina may be linked to nuclear pore related alternatively spliced isoform of Biology, Vienna Biocenter, University of Vienna, Dr baskets through Nup153. LAP2, sharing only the N-terminus with Bohrgasse 9, A-1030 Vienna, Austria the other isoforms. In contrast to LAP2β, (e-mail: [email protected]) Various integral membrane proteins of LAP2α is localized in the nuclear Journal of Cell Science 114, 3791-3792 (2001) the INM are also components of the interior and forms complexes with A- © The Company of Biologists Ltd lamina. The lamin B receptor (LBR) type lamins. Three proteins (all LAP2 contains eight transmembrane domains isoforms, emerin and MAN1) are The nuclear lamina is a scaffolding and binds to B-type lamins (B-type- members of a family defined by a 43- structure at the nuclear periphery and is lamin-mediated interactions involving residue ‘LEM domain’ near the N- required for maintenance of nuclear the lamina and INM proteins are shown terminus, which is involved in binding to shape, spacing of nuclear pore com- in green; La B). Nurim has five trans- a chromosomal protein, barrier to plexes, organization of heterochromatin, membrane domains, and MAN1 has two autointegration factor (BAF). In DNA replication, and regulation of predicted membrane-spanning regions. addition, LBR binds to heterochromatin transcription factors. The lamina is Their interaction with lamins has not protein 1 (HP1), and LBR and LAP2β formed by type V intermediate filament been analyzed yet. Three isoforms of interact with HA95, a chromosomal proteins, A- and B-type lamins, which lamina-associated polypeptide 1 protein that has homology to nuclear A- assemble to form a meshwork of 10-nm (LAP1A, LAP1B and LAP1C), emerin, kinase anchoring protein. Thus, LEM- filaments underneath the inner nuclear and at least four alternatively spliced domain proteins, LBR and lamins, which membrane (INM). B-type lamins are isoforms of LAP2 (β, ε, δ and γ) are type also bind to chromatin, may be involved constitutively expressed in all somatic II integral membrane proteins that each in higher-order chromatin organization. cells and contain a stable C-terminal have a nuclear N-terminus and a single Recently an INM protein that has nine

(See poster insert) 3792 JOURNAL OF CELL SCIENCE 114 (21) membrane-spanning domains, ring activity and cell cycle progression. A- Aside from the integral membrane finger binding protein (RFBP), an kinase-anchoring protein AKAP149 is a proteins of the lamina, POM121 and gp atypical type IV ATPase, was described protein of the endoplasmic reticulum and 210 have been identified as trans- to interact with RUSH, a member of the outer nuclear membrane (ONM), which membrane components of the nuclear SWI/SNF family of transcription factors associates also with the phosphatase PP1 pore complex. that remodel chromatin. and is important for post-mitotic lamin assembly. − α A-type-lamin LAP2 complexes inter- Cell Science at a Glance on the Web act with the retinoblastoma protein (pRb), LBR was identified as part of a huge Electronic copies of the poster insert are whereas LAP2β binds to mouse germ cell complex that also contains the integral available in the online version of this article less (mGCL), which interacts with the membrane protein p18, an LBR kinase at jcs.biologists.org. JPEG and PDF files transcription factor E2F-associated DP. and p32/34, a low-molecular-weight (see supplemental material) can be downloaded for printing or use as slides. Thus, these proteins might regulate E2F protein.

Year 2001 Travelling Fellowships

JCS offers fellowships of up to US$4000 to graduate students and post-docs wishing

to make collaborative visits to other laboratories. These are designed to cover the cost

of travel and other expenses, and there is no restriction on nationality. Applicants

should be working in the field of cell biology and intend to visit a laboratory in another

country. Each application is judged on the excellence of the candidate, and the

importance and innovative quality of the work to be done.

Application forms can be downloaded from our Web site at http://jcs.biologists.org.

Please send the completed application form, together with a copy of your CV, an account

of the work to be done and a breakdown of the costs involved, as well as letters of

recommendation from the heads of the laboratory in which you currently work and the

laboratory you hope to visit, to the Production Editor at the address below.

Journal of Cell Science Editorial Office,

The Company of Biologists Limited,

Bidder Building, 140 Cowley Road, Cambridge CB4 0DL, UK

Deadline: 31 December 2001