Calreticulin Is a Negative Regulator of Bronchial Smooth Muscle Cell Proliferation
Figure 1
(a) Simplified scheme of the CEBPA mRNA. Due to alternative translation start sites (A, B, and C), full length (p42) and truncated (p30) C/EBPα proteins with distinct functions can be formed. Start site B is out of frame and determines whether A or B is accessible for translation, hence producing either p42 or p30 C/EBPα proteins. (b) Schematic representation showing three important signaling pathways for the translation control of CEBPA messenger RNA: (1) the pathway leading to activation of the eukaryotic initiation factors eIF2 and eIF2B, which is counteracted by hnRNPE2, (2) the pathway of mTOR and eukaryotic initiation factor 4E (eIF4E), which is inhibited by 4E-BP1, and (3) the pathway leading to calreticulin (CRT) expression, a protein that binds to a double-stranded RNA loop and prevents the translation of full length C/EBPα proteins. Abbreviations: 5′ TOP: 5′ tract of pyrimidine; mTOR: mammalian target of rapamycin.
