title: Alternative splicing in protein associated with Myc (Pam) influences its binding to c-Myc.
abstract: We recently identified Pam (for protein associated with c-Myc), as a binding partner for the tuberous sclerosis complex (TSC) protein tuberin in brain. The highly conserved Pam homologs in Drosophila and C. elegans are neuron-specific proteins that regulate synaptic growth. The Pam gene contains 83 exons and encodes a 4,641-amino-acid polypeptide with a predicted molecular weight of approximately 510 kDa. In a previous study, we demonstrated that Pam is expressed as two forms, approximately 450 kDa in rat embryonic and a approximately 350 kDa in rat adult brain. Here we have extended that work to show the approximately 450 kDa form is expressed in rat embryonic kidney, heart, and lung and in rat cell lines, and the approximately 350 kDa form is expressed in adult rat tissues as well as in human and mouse brain and human and mouse cell lines. To understand the size difference, we investigated alternative splicing of Pam in brain and detected six isoforms in the Myc-binding region resulting from splicing of exon 53, and three new exons, 52A, 56, and 56A. We also demonstrate that the presence of exon 52A in Pam significantly enhances binding to Myc, suggesting functional importance of this alternative splicing. The presence of Pam in many cellular compartments, its spliced variants, as well as its multiple binding partners, including tuberin, make it a complex, yet intriguing protein in the nervous system.
authors.affiliation: Molecular Neurogenetics Unit and Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
authors.forename: Túlio M
authors.initials: TM
authors.lastname: Santos
authors.forename: Sangyeul
authors.initials: S
authors.lastname: Han
authors.forename: Mark
authors.initials: M
authors.lastname: Bowser
authors.forename: Karen
authors.initials: K
authors.lastname: Sazani
authors.forename: Roberta L
authors.initials: RL
authors.lastname: Beauchamp
authors.forename: Vanishree
authors.initials: V
authors.lastname: Murthy
authors.forename: Pradeep G
authors.initials: PG
authors.lastname: Bhide
authors.forename: Vijaya
authors.initials: V
authors.lastname: Ramesh
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern / Q000379:methods; D015153:Blotting, Western / Q000379:methods; D001921:Brain / Q000033:anatomy & histology / Q000378:metabolism; D003001:Cloning, Molecular / Q000379:methods; D005091:Exons; D015870:Gene Expression / Q000502:physiology*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D007668:Kidney / Q000378:metabolism; D008168:Lung / Q000378:metabolism; D051379:Mice; D006899:Mixed Function Oxygenases / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics* / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D020033:Protein Isoforms / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D015533:Transcriptional Activation
chemical_list: D009097:Multienzyme Complexes; D020033:Protein Isoforms; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D006899:Mixed Function Oxygenases; C035189:peptidylglycine monooxygenase