title: Cloning of a newly identified heart-specific troponin I isoform, which lacks the troponin T binding portion, using the yeast hybrid system.
abstract: OBJECTIVE
  To elucidate the molecular pathogenesis behind increased levels of laminin in cardiac muscle cells in cardiomyopathy by using a yeast hybrid screen. The present study reports the cloning of a newly identified heart-specific troponin I isoform, which is putatively linked to laminin. Future studies will explore the functional significance of this connection.
  
  
  METHODS
  Yeast two-hybrid screen analysis was performed using MLF1-interacting protein (amino acids 1 to 318) as bait. The human heart complementary DNA library was screened by using the yeast-mating method for overnight culture.
  
  
  RESULTS
  Two final positive clones from the heart library were isolated. These two clones encoded the same protein, a short isoform of human cardiac troponin I (TnI) that lacked TnI exons 5 and 6. The TnI isoform has a heart-specific expression pattern and it shares several sequence features with human cardiac TnI; however, it lacks the troponin T binding portion.
  
  
  CONCLUSIONS
  The heart-specific segment of the human cardiac TnI isoform shares several sequence features with human cardiac TnI, but it lacks the troponin T binding portion. These results suggest that the heart-specific TnI isoform may be involved in cardiac development and disease.
authors.affiliation: Departments of Internal Medicine and.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Suzuki
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Arakawa
authors.forename: Masaki
authors.initials: M
authors.lastname: Ito
authors.forename: Hisashi
authors.initials: H
authors.lastname: Yamada
authors.forename: Junko
authors.initials: J
authors.lastname: Horiguchi-Yamada