Abstract
Ran/TC4, referred to here as Ran1, is a 25-kilodalton nuclear GTP-binding protein with an acidic C terminus that lacks any consensus prenylation sites. Here, we use a nitrocellulose overlay assay to identify potential effector proteins that bind specifically and with high affinity to the GTP-bound form of Ran1. GTP-Ran1 is shown to bind a variety of proteins, present in many eukaryotic tissues and cell extracts. A 28-kDa protein is cytosolic, whereas others, consisting of proteins of 86-300 kDa, are primarily localized in the nucleus. Binding is highly specific and is not detected by other small GTPases, such as c-Ha-Ras or Rab3A. Both deletion of the C-terminal-DEDDDL acidic sequence or alteration of the N terminus of Ran1 inhibits binding. However, these altered forms of Ran1 maintain the capacity to bind guanyl nucleotides and interact with the nucleotide exchange factor. The Ran1-binding proteins potently inhibit release of GTP from Ran1. These proteins can therefore maintain Ran1 in the "on" state and are potential down-stream effectors for Ran1-dependent cellular processes.
Highlights
RanpTC4, referred to here as Ranl, is a 25-kilodalton temperature-induced lossof RCCl occurs duringS phase or G1 nuclear GTP-binding proteinwith an acidic C terminus phase [11, 12]
The Ranl-binding proteins potently inhibit re- been demonstrated in tsBN2 cells upon temperature-induced lease ofGTPfrom Ranl. These proteins can loss of RCCl [18].Whether these functions are related tothe maintain Ranl in the “on”state and are potential down-RCC1-associated cell cycle phenomena is not known; stream effectors foRr ad-dependent cellular processes. the mRNA transport effects occur in minutes versus the cell cycle effects, which occuirn hours
Whereasthe cell cycle events are dependent upon p34cdc28 kinase activation, Ranl’ was initialliydentified as the gene product of TC4, an the nuclear transport effects are not [11]
Summary
RanpTC4, referred to here as Ranl, is a 25-kilodalton temperature-induced lossof RCCl occurs duringS phase or G1 nuclear GTP-binding proteinwith an acidic C terminus phase [11, 12]. Residual GDP bound after30 min can be attributed to nonspe- the resultant supernatant protein was separated by SDS-PAGE and cific binding to the nitrocellulose filters by the nuclear extract.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
