An Extensive Requirement for Transcription Factor IID-specific TAF-1 in Caenorhabditis elegans Embryonic Transcription

Amy K Walker,Yang Shi,T Keith Blackwell

doi:10.1074/jbc.m310731200

Amy K Walker, Yang Shi + Show 1 more

Open Access

https://doi.org/10.1074/jbc.m310731200

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Abstract

The general transcription factor TFIID sets the mRNA start site and consists of TATA-binding protein and associated factors (TAF(II)s), some of which are also present in SPT-ADA-GCN5 (SAGA)-related complexes. In yeast, results of multiple studies indicate that TFIID-specific TAF(II)s are not required for the transcription of most genes, implying that intact TFIID may have a surprisingly specialized role in transcription. Relatively little is known about how TAF(II)s contribute to metazoan transcription in vivo, especially at developmental and tissue-specific genes. Previously, we investigated functions of four shared TFIID/SAGA TAF(II)s in Caenorhabditis elegans. Whereas TAF-4 was required for essentially all embryonic transcription, TAF-5, TAF-9, and TAF-10 were dispensable at multiple developmental and other metazoan-specific promoters. Here we show evidence that in C. elegans embryos transcription of most genes requires TFIID-specific TAF-1. TAF-1 is not as universally required as TAF-4, but it is essential for a greater proportion of transcription than TAF-5, -9, or -10 and is important for transcription of many developmental and other metazoan-specific genes. TAF-2, which binds core promoters with TAF-1, appears to be required for a similarly substantial proportion of transcription. C. elegans TAF-1 overlaps functionally with the coactivator p300/CBP (CBP-1), and at some genes it is required along with the TBP-like protein TLF(TRF2). We conclude that during C. elegans embryogenesis TAF-1 and TFIID have broad roles in transcription and development and that TFIID and TLF may act together at certain promoters. Our findings imply that in metazoans TFIID may be of widespread importance for transcription and for expression of tissue-specific genes.

Highlights

Eukaryotic mRNA transcription involves formation of a preinitiation complex (PIC)1 at the core promoter, which directs initiation
TAF-1 is unique to TFIID, but many other TAFIIs are found in the SPT-ADA-GCN5 (SAGA)related complexes [5, 6], which are similar in structure to TFIID but lack TATA-binding protein (TBP) and contain a GCN5-related histone acetyltransferase instead of TAF-1
Expression of the majority of yeast genes is prevented by conditional loss of either TAF-9, which is shared between TFIID and SAGA, or of Taf-1 and the SAGA histone acetyltransferase GCN5 simultaneously, suggesting that TFIID and SAGA are redundant at many genes (4 – 6)

Summary

EXPERIMENTAL PROCEDURES

C. elegans and Bioinformatics—C. elegans strains were provided to us and maintained as described previously [22]. RNAi Analysis—For injection of dsRNA, cDNA fragments for taf-1 (nucleotides 3066 –3942 and 4329 – 4936) and taf-2 (nucleotides 385– 1347) were generated by PCR from a C. elegans cDNA library (gift of Marc Vidal). For feeding of dsRNA, cDNA fragments for taf-1 (nucleotides 2791–3408) and ama-1 (nucleotides 1254 –2259) were inserted into the feeding vector pPD129.36 (gift of Andy Fire). Synchronized L4 larvae were placed on bacteria expressing dsRNA to gfp (pPD128.110, gift of Andy Fire), ama-1, or taf-1 for 36 h. Taf-1 and ama-1(RNAi) embryos produced from feeding dsRNA at 36 h had antiphospho-Ser-2 staining patterns and LET-858::GFP expression similar to injected dsRNA at 24 h (not shown). CDNA was produced from 1 ␮g of control RNA and from equivalent numbers of ama-1 or taf-1(RNAi) embryos (Superscript II, Invitrogen).

RESULTS

Findings

DISCUSSION