Transcript assemblers from RNA-seq reads

Hi all,

I would like to examine the complete transcripts sequence of specific genes on the RNA-seq. As input, I can use the RNA-seq FASTQ file.
for example: Looking at all BRAF transcripts full transcript (all cDNA combinations) on the FASTQ file (could be pair end or not)

What will be the recommended way to do so?
It will be great if I could avoid processing the whole sequence at some point of the processing pipeline and focus on the requested gene.

Many thanks,
Eila