title: MCL-1S, a splicing variant of the antiapoptotic BCL-2 family member MCL-1, encodes a proapoptotic protein possessing only the BH3 domain.
abstract: MCL-1 (myeloid cell leukemia-1) is an antiapoptotic BCL-2 family protein discovered as an early induction gene during myeloblastic leukemia cell differentiation. This survival protein has the BCL-2 homology (BH) domains 1, 2, and 3 and a C-terminal transmembrane region. We identified a short splicing variant of the MCL-1 mRNA in the human placenta encoding a protein, termed MCL-1 short (MCL-1S), with an altered C terminus as compared with the full-length MCL-1 long (MCL-1L), leading to the loss of BH1, BH2, and the transmembrane domains. Analysis of the human MCL-1 gene indicated that MCL-1S results from the splicing out of exon 2 during mRNA processing. MCL-1S, unlike MCL-1L, does not interact with diverse proapoptotic BCL-2-related proteins in the yeast two-hybrid system. In contrast, MCL-1S dimerizes with MCL-1L in the yeast assay and coprecipitates with MCL-1L in transfected mammalian cells. Overexpression of MCL-1S induces apoptosis in transfected Chinese hamster ovary cells, and the MCL-1S action was antagonized by the antiapoptotic MCL-1L. Thus, the naturally occurring MCL-1S variant represents a new proapoptotic BH3 domain-only protein capable of dimerizing with the antiapoptotic MCL-1L. The fate of MCL-1-expressing cells could be regulated through alternative splicing mechanisms and interactions of the resulting anti- and proapoptotic gene products.
authors.affiliation: Division of Reproductive Biology, Department of Gynecology and Obstetrics, Stanford University School of Medicine, CA 94305-5317, USA.
authors.forename: J
authors.initials: J
authors.lastname: Bae
authors.forename: C P
authors.initials: CP
authors.lastname: Leo
authors.forename: S Y
authors.initials: SY
authors.lastname: Hsu
authors.forename: A J
authors.initials: AJ
authors.lastname: Hsueh
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D016466:CHO Cells; D003001:Cloning, Molecular; D006224:Cricetinae; D018076:DNA, Complementary / Q000378:metabolism; D019281:Dimerization; D005091:Exons; D020224:Expressed Sequence Tags; D015723:Gene Library; D006801:Humans; D008957:Models, Genetic; D008969:Molecular Sequence Data; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D010920:Placenta / Q000737:chemistry; D011233:Precipitin Tests; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D019253:Proto-Oncogene Proteins c-bcl-2; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D020798:Two-Hybrid System Techniques
chemical_list: D018076:DNA, Complementary; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D020033:Protein Isoforms; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger