Database of mutations within the adenovirus 5 E1A oncogene
- Departments of Oncology and Pharmacology & Toxicology, The University of Western Ontario, London Regional Cancer Centre, 790 Commissioners Road East, London, Ontario N6A 4L6, Canada
- Tel: +1 519 685 8617; Fax: +1 519 685 8616; Email: jmymryk{at}julian.uwo.ca
- Received August 15, 1997.
- Accepted September 24, 1997.
Abstract
The Ad5 E1A database is a listing of mutations affecting the early region 1A (E1A) proteins of human adenovirus type 5. The database contains the name of the mutation, the nucleic acid sequence changes, the resulting alterations in amino acid sequence and reference. Additional notes and references are provided on the effect of each mutation on E1A function. The database is contained within the Adenovirus 5 E1A page on the World Wide Web at:http://www.geocities.com/CapeCanaveral/Hangar/2541/
Introduction
The proteins encoded by early region 1A (E1A) of human adenovirus type 5 (Ad5) are useful tools with which to investigate the regulation of cell growth and development. In the infected cell, the E1A proteins act as potent regulators of viral and cellular gene transcription to establish an optimal environment for viral replication. The multi-functional E1A proteins also induce quiescent cells to enter and traverse the cell cycle, block differentiation, immortalize primary rodent cells and transform them in co-operation with a second oncogene (1–5). Besides these oncogenic properties, E1A can also function as an anti-oncogene to suppress transformation, metastasis and tumorigenicity and induce apoptosis (6,7). These many functions have made E1A a powerful tool to dissect cellular regulatory processes.
Five distinct mRNA products are produced from the primary E1A transcript by alternative splicing (8–10) (Fig. 1A). These encode two major proteins of 289 and 243 residues (R), and several less abundant E1A proteins (Fig. 1B). With the exception of the 9S E1A mRNA, the reading frame of each mRNA remains conserved after splicing. Thus, the 243, 217 and 171R E1A proteins represent edited versions of the larger 289R E1A protein. Comparison of the E1A sequence of a number of adenovirus serotypes has identified three regions of sequence conservation (11,12), designated conserved regions (CR) 1, 2 and 3 (Fig. 1B). These regions play important roles in mediating many E1A activities (1–5).
The E1A proteins are not sequence specific DNA binding proteins, but instead act by binding to a variety of cellular proteins, including members of the p300 and pRB family of regulatory proteins (1–5). By targeting these and other cellular proteins, E1A alters or inhibits their normal functions in the cell, thereby reprogramming growth and development.
Schematic representation of the structure of the E1A transcription and translation products. (A) The primary E1A transcript is alternatively spliced to generate five mRNA products ranging in size from 13S to 9S. The locations of the cap, translation start, translation stop, polyadenylation and splicing sites are indicated at the top. Coding regions are represented as filled rectangles. (B) The E1A gene encodes five related proteins ranging in size from 289 to 55 residues (R). Three regions of amino acid sequence that are conserved between the E1A proteins of various adenovirus serotypes are indicated as stippled, hatched or solid rectangles, respectively. The boundaries of these three conserved regions (CR) are labelled with respect to their locations in the 289R E1A product. The sequence of the second exon encoded portion of the 55R product differs from that of the other E1A proteins due to a change in reading frame, and this is indicated by the shaded rectangle.
Studies of E1A function have been greatly facilitated by the use of E1A mutants. Analyses of the phenotypes of a battery of mutants have established strong correlations between various E1A activities and identified important links between E1A function and its association with cellular factors (1–5). Mutational analyses have further demonstrated that E1A is a modular protein, containing multiple domains that can function independently, and sometimes redundantly, to provoke changes in cell regulation (1,5). Intriguingly, domains homologous to those first identified in E1A by mutational analysis have been found in a number of other viral (13–15) and cellular (16–21) proteins, providing immediate insight into their mechanism of action.
Sample from the database of Ad5 E1A mutations
Database Content
The database of mutations within the Ad5 E1A oncogene is intended as a resource for researchers using E1A to investigate mechanisms of cell regulation. The database was compiled from an extensive search of the literature and contains an ordered listing of >400 E1A mutants constructed in laboratories throughout the world. The database contains the name of the mutation, the nucleic acid sequence changes of the mutation (where available), the resulting alterations in amino acid sequence (where available) and reference (Table 1). Additional notes and references are provided on the effect of the mutation on E1A function. Although not yet comprehensive, the database continues to grow and additional mutants are added as information becomes available. This database should be a valuable resource for those interested in using E1A to study cellular processes.
Database Availability
The database of mutations affecting the Ad5 E1A proteins is contained within the Adenovirus 5 E1A page on the World Wide Web at http://www.geocities.com/CapeCanaveral/Hangar/2541/. In order to make it as useful as possible, I encourage others in the field to provide additions and corrections, which can be submitted using the electronic form provided within the database, or alternatively can be emailed to myself at: jmymryk{at}julian.uwo.ca.
Acknowledgements
I would like to thank Dr S.T. Bayley for introducing me to the E1A proteins of Ad5. I also thank Geocities for providing web space for the Ad5 E1A page and Database.
- © 1998 Oxford University Press
