The elongation factors Pandora/Spt6 and Foggy/Spt5 promote transcription in the zebrafish embryo

Abstract

Precise temporal and spatial control of transcription is a fundamental component of embryonic development. Regulation of transcription elongation can act as a rate-limiting step during mRNA synthesis. The mechanisms of stimulation and repression of transcription elongation during development are not yet understood. We have identified a class of zebrafish mutations (pandora, sk8 and s30) that cause multiple developmental defects, including discrete problems with pigmentation, tail outgrowth, ear formation and cardiac differentiation. We demonstrate that the pandora gene encodes a protein similar to Spt6, a proposed transcription elongation factor. Additionally, the sk8 and s30 mutations are null alleles of the foggy/spt5 locus, which encodes another transcription elongation factor. Through real-time RT-PCR analysis, we demonstrate that Spt6 and Spt5 are both required for efficient kinetics of hsp70 transcription in vivo. Altogether, our results suggest that Spt6 and Spt5 play essential roles of comparable importance for promoting transcription during embryogenesis. This study provides the first genetic evidence for parallel functions of Spt6 and Spt5 in metazoans and establishes a system for the future analysis of transcription elongation during development. Supplemental figure available on-line

The conserved histone chaperone Spt6 is strongly required for DNA replication and genome stability

“…Spt6 is a highly conserved histone chaperone of great biological importance. It is essential for viability in S. cerevisiae , 6 , 7 and it is required for proper development in C. elegans , 8 zebra-fish, 9 , 10 and Drosophila . 11 , 12 In mammalian systems, Spt6 is required for embryonic stem cell maintenance, muscle cell differentiation, epithelial cell differentiation, and immunoglobulin class-switch recombination.…”

Two deltaC splice-variants have distinct signaling abilities during somitogenesis and midline patterning

“…To compare levels of deltaC transcripts between genotypes, deltaC levels were normalized to β-actin expression. β-actin control primers were as previously described (Keegan et al, 2002).…”

Rtf1-dependent transcriptional pausing regulates cardiogenesis

“…Spt6 (Suppressor of Ty 6) is a histone chaperone that promotes RNA Polymerase II elongation and co-transcriptionally modulates chromatin structure 14,15 . In zebrafish, loss of function of Spt6 disrupts cardiomyocyte differentiation and interacts genetically with the transcriptional pausing/elongation factor Spt5 (Suppressor of Ty 5) to support Nkx2.5+ cardiac progenitor specification 16 . While both Spt6 and Spt5 promote transcription elongation, they likely do so via distinct mechanisms.…”