Related Experiment Video
Updated: Aug 24, 2026

Toeprinting Analysis of Translation Initiation Complex Formation on Mammalian mRNAs
Published on: May 10, 2018
betaPix-b(L), a novel isoform of betaPix, is generated by alternative translation
Sangmyung Rhee1, Soo Jung Yang, Seung Joon Lee
1School of Biological Sciences, Seoul National University, Seoul 151-742, South Korea.
Abstract:
betaPix (Pak-interacting exchange factor) isoforms are recently identified guanine nucleotide exchange factors (GEFs) for Rho family GTPases, Rac/Cdc42, that are key players in the regulation of actin dynamics. Here we show that a novel 105-kDa betaPix isoform, betaPix-bL, is generated by alternative translation of betaPix-b mRNA. Translation of betaPix-bL starts at an atypical initiation site, GTG, that is located 57 nucleotides downstream from the newly identified 5' end of betaPix-b cDNA. The expression of two isoforms, betaPix-b and betaPix-bL, from betaPix-b mRNA is controlled by an internal ribosome entry site (IRES)-driven mechanism. Comparing to betaPix-b, betaPix-bL contains additional 105 amino acids composed of a calponin homology (CH) domain and a serine-rich sequence in the N-terminus. The expression of betaPix-bL in rat brain is developmentally regulated and high in the embryonic stages, suggesting that the function of betaPix-bL is more heavily required during the early stages of brain development.
Related Concept Videos
Leaky Scanning
RNA Splicing
Ribosome Profiling
Applications of ribosome profiling
Ribosome profiling has many applications, including in vivo monitoring of translation inside a particular organ or tissue type and quantifying new protein synthesis levels.
The technique helps...
Initiation of Translation
First, the initiator tRNA must be selected from the pool of elongator tRNAs by eukaryotic initiation factor 2 (eIF2). The initiator tRNA (Met-tRNAi) has conserved sequence elements including modified bases at...
Post-translational Translocation of Proteins to the RER
Targeting proteins to the ER
Hsp40 and Hsp70 chaperone molecules bind the translated proteins in the cytosol to prevent their folding. The chaperone binding helps to keep the signal...
What is Gene Expression?

