What is the relationship between the Dynamic Language Runtime and C# 4.0?

Question

Let's say I wanted to create a dynamic language compiler/interpreter, a Scheme interpreter perhaps, on the .NET platform as it exists today. Would I be better off using the Dynamic Language Runtime (DLR), or using C# 4.0 to implement my language's dynamic features? Or do I need both?

I know that there has been other work done in this area, in particular with IronScheme and IronPython. Both of those languages use the DLR; I believe IronPython uses the most current version of the DLR (which is about a year old), while IronScheme uses an early, heavily modified fork of an early version of the DLR. But C# 4.0 was not available when these compilers were created.

I've seen Rob Conery's work with Massive, using C# 4.0's dynamic features; it is quite impressive. But would C# hold up to the full-scale effort of a dynamic language compiler/intepreter? Are there features in the DLR that are missing from C#, or was the DLR essentially rolled into C# 4.0? Would I be missing any important features of the DLR if I just used C# 4.0 exclusively?