Báo cáo khoa học: Neural retina leucine-zipper regulates the expression of Ppp2r5c, the regulatory

Neural retina leucine-zipper regulates the expression of

Ppp2r5c, the regulatory subunit of protein

phosphatase 2A, in photoreceptor development

Jung-Woong Kim, Sang-Min Jang, Chul-Hong Kim, Joo-Hee An, Eun-Jin Kang and

Kyung-Hee Choi

Department of Life Science (BK21 program), College of Natural Sciences, Chung-Ang University, Seoul, Korea

Introduction

Protein phosphatase 2A (PP2A) is a major cellular ser￾ine ⁄threonine phosphatase that plays a critical role in

balancing phosphorylation signals that are important

for cellular proliferation and differentiation [1,2]. The

catalytic C-subunit of PP2A associates with the scaf￾folding A-subunit, and the A⁄ C heterodimer also binds

to regulatory B-subunits to form a heterotrimeric holo￾enzyme [3]. B-subunits can be divided into four distinct

families on the basis of their homology, namely B

(B55 or PR55) [4–7], B¢ (B56 or PR61) [8–11], B¢¢

(PR48 ⁄ 59 ⁄ 72 ⁄ 130) [12,13] and B¢¢¢ (PR93 ⁄ 110) [14],

and the B56 family consists of at least five different

gene products, a (PPP2R5A), b (PPP2R5B), c (PPP2R5C),

d (PPP2R5D), and e (PPP2R5E) [8]. The five B56 fam￾ily members have diverse functions, including a mitotic

checkpoint in Xenopus laevis and binding to APC pro￾tein, which acts as a scaffold for b-catenin, axin and

glycogen synthase kinase-b [15,16]. Moreover, B56e is

involved in Xenopus eye development through the insu￾lin-like growth factor–phosphoinositide 3-kinase–Akt

and hedgehog signaling pathways [17]. It is believed

that PP2A exercises regulatory flexibility and substrate

specificity through association of the core A⁄ C hetero￾dimer with one of the regulatory B-subunits [1,18].

This characteristic of PP2A contributes to its ability

to regulate multiple cellular functions; however, the

Keywords

neural retina leucine-zipper; photoreceptor

development; PP2A regulatory subunit;

Ppp2r5c; target gene

Correspondence

K.-H. Choi, Department of Life Science

(BK21 program), College of Natural

Sciences, Chung-Ang University, 221

Heuksuk Dong, Dongjak Ku, Seoul 156-756,

South Korea

Fax: +82 2 824 7302

Tel: +82 2 820 5209

E-mail: [email protected]

(Received 12 July 2010, revised 11

September 2010, accepted 11 October

2010)

doi:10.1111/j.1742-4658.2010.07910.x

Protein phosphatase 2A plays an important role in balancing phosphoryla￾tion signals that are critical for cell proliferation and differentiation. Here,

we report that Ppp2r5c (regulatory subunit of protein phosphatase 2A)

expression was regulated by the transcription factor neural retina leucine￾zipper (Nrl) through enhancement of its transcriptional activity on the

Ppp2r5c promoter. Using electrophoretic mobility shift assays and chroma￾tin immunoprecipitation, we also found that Nrl bound directly to the

Nrl-response element on the Ppp2r5c promoter. The affinity of binding of

Nrl to the Ppp2r5c promoter was tightly regulated during mouse photo￾receptor development. Overall, these results suggest that Ppp2r5c expres￾sion is regulated by Nrl during retinogenesis through direct binding to the

promoter region of Ppp2r5c.

Abbreviations

ChIP, chromatin immunoprecipitation; E, embryonic day; EMSA, electrophoretic mobility shift assay; GST, glutatione S-transferase;

NRE, neural retina leucine-zipper-response element; Nrl, neural retina leucine-zipper; NS, not significant; P, postnatal day; PP2A, protein

phosphatase 2A; siRNA, small interfering RNA; WT, wild type.

FEBS Journal 277 (2010) 5051–5060 ª 2010 The Authors Journal compilation ª 2010 FEBS 5051