Since Ross (1967), movement has been known to display what is called the island-sensitivity. As has long been advocated and assumed in the generative grammar, English DP and TP are the cyclic nodes/bounding nodes/barriers from which an extraction is disallowed, which turns into different versions of locality in the name of Phase Impenetrability Condition (PIC) in Chomsky (2000, 2001). With this technology, the bounding nodes enter into a new stage, Phases. In essence, however, Cyclicity, Subjacency, and PIC are all dealing with locality constraint on movement (Boecks 2012:58). While maintaining a theory-neutral stance between different versions of locality constraint on Wh-movement, the purpose of this paper is to highlight the two closely related constructions of English, Sentential Subject Construction (SSC) and its corresponding Extraposition Construction (EC) with respect to the island effect. The fact that Wh-constituent can be extracted neither from finite that-CP nor non-finite for-CP in SSC, while it freely moves out of both that-CP and for-CP in EC is analyzed with a null D head. As a consequence of this analysis, it is argued that a null D(P) is a necessary constituent in order to account for the impossibility of Wh-extraction from SSC. On the other hand, the ban on extraction is lifted in EC, due to the lack of the encapsulating DP.